

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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).

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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 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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.