

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.

###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.