Unidirectional spin Hall magnetoresistance (USMR) is a magnetoresistance effect with potential applications to read two-terminal spin–orbit-torque (SOT) devices directly. In this work, we observed a large USMR value (up to 0.7 × 10−11 per A/cm2, 50% larger than reported values from heavy metals) in sputtered amorphous PtSn4/CoFeB bilayers. Ta/CoFeB bilayers with interfacial MgO insertion layers are deposited as control samples. The control experiments show that increasing the interfacial resistance can increase the USMR value, which is the case in PtSn4/CoFeB bilayers. The observation of a large USMR value in an amorphous spin–orbit-torque material has provided an alternative pathway for USMR application in two-terminal SOT devices.

1.
I. M.
Miron
,
G.
Gaudin
,
S.
Auffret
 et al, “
Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer
,”
Nat. Mater.
9
(
3
),
230
234
(
2010
).
2.
L.
Liu
,
T.
Moriyama
,
D. C.
Ralph
 et al, “
Spin-torque ferromagnetic resonance induced by the spin Hall effect
,”
Phys. Rev. Lett.
106
(
3
),
036601
(
2011
).
3.
X.
Fan
,
H.
Celik
,
J.
Wu
 et al, “
Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers
,”
Nat. Commun.
5
(
1
),
3042
(
2014
).
4.
J.
Ding
,
C.
Liu
,
V.
Kalappattil
 et al, “
Switching of a magnet by spin–orbit torque from a topological Dirac semimetal
,”
Adv. Mater.
33
(
23
),
2005909
(
2021
).
5.
K.
Tang
,
Z.
Wen
,
Y.-C.
Lau
 et al, “
Magnetization switching induced by spin–orbit torque from Co2MnGa magnetic Weyl semimetal thin films
,”
Appl. Phys. Lett.
118
(
6
),
062402
(
2021
).
6.
Q.
Shao
,
P.
Li
,
L.
Liu
 et al, “
Roadmap of spin-orbit torques
,”
IEEE Trans. Magn.
57
,
1
39
(
2021
).
7.
S.
Zhang
,
S.
Luo
,
N.
Xu
 et al, “
A spin–orbit‐torque memristive device
,”
Adv. Electron. Mater.
5
(
4
),
1800782
(
2019
).
8.
J. M.
Lee
,
K.
Cai
,
G.
Yang
 et al, “
Field-free spin–orbit torque switching from geometrical domain-wall pinning
,”
Nano Lett.
18
(
8
),
4669
4674
(
2018
).
9.
L.
Liu
,
O. J.
Lee
,
T. J.
Gudmundsen
 et al, “
Current-induced switching of perpendicularly magnetized magnetic layers using spin torque from the spin Hall effect
,”
Phys. Rev. Lett.
109
(
9
),
096602
(
2012
).
10.
L.
Liu
,
C.-F.
Pai
,
Y.
Li
 et al, “
Spin-torque switching with the giant spin Hall effect of tantalum
,”
Science
336
(
6081
),
555
558
(
2012
).
11.
C. O.
Avci
,
A.
Quindeau
,
C.-F.
Pai
 et al, “
Current-induced switching in a magnetic insulator
,”
Nat. Mater.
16
(
3
),
309
314
(
2017
).
12.
Y.-C.
Lau
,
D.
Betto
,
K.
Rode
 et al, “
Spin–orbit torque switching without an external field using interlayer exchange coupling
,”
Nat. Nanotechnol.
11
(
9
),
758
762
(
2016
).
13.
Y.
Fan
,
P.
Upadhyaya
,
X.
Kou
 et al, “
Magnetization switching through giant spin–orbit torque in a magnetically doped topological insulator heterostructure
,”
Nat. Mater.
13
(
7
),
699
704
(
2014
).
14.
J.-P.
Wang
,
S. S.
Sapatnekar
,
C. H.
Kim
 et al, “
A pathway to enable exponential scaling for the beyond-CMOS era
,” in
Proceedings of the 54th Annual Design Automation Conference 2017
,
2017
.
15.
C.-H.
Hsu
,
J.
Karel
,
N.
Roschewsky
 et al, “
Spin-orbit torque generated by amorphous FeSi
,” e-print arXiv:2006.07786 (
2020
).
16.
T.-C.
Wang
,
T.-Y.
Chen
,
C.-T.
Wu
 et al, “
Comparative study on spin–orbit torque efficiencies from W/ferromagnetic and W/ferrimagnetic heterostructures
,”
Phys. Rev. Mater.
2
(
1
),
014403
(
2018
).
17.
Y.
Wu
,
L.-L.
Wang
,
E.
Mun
 et al, “
Dirac node arcs in PtSn4
,”
Nat. Phys.
12
(
7
),
667
671
(
2016
).
18.
J.
Yan
,
X.
Luo
,
J. J.
Gao
 et al, “
The giant planar Hall effect and anisotropic magnetoresistance in Dirac node arcs semimetal PtSn4
,”
J. Phys.: Condens. Matter
32
(
31
),
315702
(
2020
).
19.
A.
Bose
,
J. N.
Nelson
,
X. S.
Zhang
 et al, “
Effects of anisotropic strain on spin–orbit torque produced by the Dirac nodal line semimetal IrO2
,”
ACS Appl. Mater. Interfaces
12
(
49
),
55411
55416
(
2020
).
20.
T.
Misawa
and
K.
Nomura
, “
Semi-quantized spin pumping and spin-orbit torques in topological Dirac semimetals
,”
Sci. Rep.
9
(
1
),
19659
(
2019
).
21.
J.
Liu
,
Y.
Fan
,
D.
Zhang
 et al, “
Element doping enhanced charge-to-spin conversion efficiency in amorphous PtSn4 Dirac semimetal
,” arXiv:2202.01384 (
2022
).
22.
C. O.
Avci
,
K.
Garello
,
A.
Ghosh
 et al, “
Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers
,”
Nat. Phys.
11
(
7
),
570
575
(
2015
).
23.
C. O.
Avci
,
G.
Kevin
,
A.
Ghosh
 et al, “
Origins of the unidirectional spin Hall magnetoresistance in metallic bilayers
,”
Phys. Rev. Lett.
121
(
8
),
087207
(
2018
).
24.
S. S.-L.
Zhang
and
G.
Vignale
, “
Theory of unidirectional spin Hall magnetoresistance in heavy-metal/ferromagnetic-metal bilayers
,”
Phys. Rev. B
94
(
14
),
140411
(
2016
).
25.
N. H.
Duy Khang
and
P. N.
Hai
, “
Giant unidirectional spin Hall magnetoresistance in topological insulator–ferromagnetic semiconductor heterostructures
,”
J. Appl. Phys.
126
(
23
),
233903
(
2019
).
26.
W. P.
Sterk
,
D.
Peerlings
, and
R. A.
Duine
, “
Magnon contribution to unidirectional spin Hall magnetoresistance in ferromagnetic-insulator/heavy-metal bilayers
,”
Phys. Rev. B
99
(
6
),
064438
(
2019
).
27.
Y.
Lv
,
J.
Kally
,
D.
Zhang
 et al, “
Unidirectional spin-Hall and Rashba–Edelstein magnetoresistance in topological insulator-ferromagnet layer heterostructures
,”
Nat. Commun.
9
(
1
),
111
(
2018
).
28.
Y.
Lv
,
J.
Kally
,
T.
Liu
 et al, “
Large unidirectional spin Hall and Rashba–Edelstein magnetoresistance in topological insulator/magnetic insulator heterostructures
,”
Appl. Phys. Rev.
9
(
1
),
011406
(
2022
).
29.
S.
Takahashi
and
S.
Maekawa
, “
Spin current, spin accumulation and spin Hall effect
,”
Sci. Technol. Adv. Mater.
9
(
1
),
014105
(
2008
).
30.
C.-F.
Pai
,
Y.
Ou
,
L. H.
Vilela-Leão
 et al, “
Dependence of the efficiency of spin Hall torque on the transparency of Pt/ferromagnetic layer interfaces
,”
Phys. Rev. B
92
(
6
),
064426
(
2015
).
31.
C.
He
,
A.
Navabi
,
Q.
Shao
 et al, “
Spin-torque ferromagnetic resonance measurements utilizing spin Hall magnetoresistance in W/Co40Fe40B20/MgO structures
,”
Appl. Phys. Lett.
109
(
20
),
202404
(
2016
).
32.
P. E.
Tannenwald
and
M. H.
Seavey
, Jr.
, “
Ferromagnetic resonance in thin films of permalloy
,”
Phys. Rev.
105
(
2
),
377
(
1957
).
33.
J. C.
Sankey
,
Y.-T.
Cui
,
J. Z.
Sun
 et al, “
Measurement of the spin-transfer-torque vector in magnetic tunnel junctions
,”
Nat. Phys.
4
(
1
),
67
71
(
2008
).
34.
M.
Djamal
,
T.
Saragi
, and
M.
Barmawi
, “
Design and development of magnetic sensors based on giant magnetoresistance (GMR) materials
,” in
Materials Science Forum
(
Trans Tech Publications Ltd
,
2006
), Vol.
517
.
35.
R. R.
Katti
, “
Giant magneto-resistive random-access memories based on current-in-plane devices
,” in
Ultrathin Magnetic Structures IV
(
Springer
,
Berlin/Heidelberg
,
2005
), pp.
219
252
.
36.
C.
Stamm
,
C.
Murer
,
Y.
Acremann
,
M.
Baumgartner
 et al, “
X-ray spectroscopy of current-induced spin-orbit torques and spin accumulation in Pt/3d-transition-metal bilayers
,”
Phys. Rev. B
100
(
2
),
024426
(
2019
).
37.
S.
Ikeda
,
K.
Miura
,
H.
Yamamoto
 et al, “
A perpendicular-anisotropy CoFeB–MgO magnetic tunnel junction
,”
Nat. Mater.
9
(
9
),
721
724
(
2010
).
38.
Y.-H.
Wang
,
W.-C.
Chen
,
S.-Y.
Yang
 et al, “
Interfacial and annealing effects on magnetic properties of CoFeB thin films
,”
J. Appl. Phys.
99
(
8
),
08M307
(
2006
).
39.
Y.
Fan
,
H.
Li
,
M.
Dc
 et al, “
Spin pumping and large field-like torque at room temperature in sputtered amorphous WTe2−x films
,”
APL Mater.
8
(
4
),
041102
(
2020
).
40.
K.
Hasegawa
,
Y.
Hibino
,
M.
Suzuki
 et al, “
Enhancement of spin-orbit torque by inserting CoOx layer into Co/Pt interface
,”
Phys. Rev. B
98
(
2
),
020405
(
2018
).
41.
S.
Li
,
X.
Zhao
,
W.
Liu
 et al, “
Modulation of spin-orbit torque induced magnetization switching in Pt/CoFe through oxide interlayers
,”
Appl. Phys. Lett.
114
(
21
),
212404
(
2019
).
42.
Y.
Yan
,
C.
Wan
,
X.
Zhou
 et al, “
Strong electrical manipulation of spin–orbit torque in ferromagnetic heterostructures
,”
Adv. Electron. Mater.
2
(
10
),
1600219
(
2016
).

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