Strong interfacial spin-orbit torque from <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">A</mi><msub><mi mathvariant="normal">u</mi><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub><mi mathvariant="normal">T</mi><msub><mi mathvariant="normal">i</mi><mi>x</mi></msub></mrow></math> alloys driven by orbital tuning in the <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>d</mi></math> band

Hyunwoo Kim; Kyoung-Whan Kim; Gyung-Min Choi

doi:10.1103/xthb-t8dh

Strong interfacial spin-orbit torque from $A u_{1 - x} T i_{x}$ alloys driven by orbital tuning in the $d$ band

Hyunwoo Kim ¹, Kyoung-Whan Kim ², and Gyung-Min Choi ^1,*

¹Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
²Department of Physics, Yonsei University, Seoul 03722, Korea

^*Contact author: gmchoi@skku.edu

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Phys. Rev. B 114, 134417 – Published 14 September, 2026

DOI: https://doi.org/10.1103/xthb-t8dh

Abstract

Conventionally, enhanced spin-orbit torque (SOT) efficiency in metallic alloy systems has been achieved by the bulk spin generation mechanism of the spin Hall effect. In this study, we investigated SOT in Au-Ti alloy. While pure Au exhibits a negligible SOT, the Au-Ti alloy exhibits a high SOT efficiency of up to 0.14. Notably, the observed SOT has a substantial interfacial contribution that is attributed to the interfacial mechanism of the Rashba-Edelstein effect. Electron transfer between Au and Ti modifies the Au $5 d$ orbital, inducing a shift in energy level and a revival of orbital momentum, which in turn is associated with Rashba spin splitting. The orbital tuning mechanisms proposed in this work highlight the potential of an orbital-engineering approach for SOT.

Physical Review B

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Strong interfacial spin-orbit torque from $A u_{1 - x} T i_{x}$ alloys driven by orbital tuning in the $d$ band

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Strong interfacial spin-orbit torque from Au1−xTix alloys driven by orbital tuning in the d band

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Strong interfacial spin-orbit torque from $A u_{1 - x} T i_{x}$ alloys driven by orbital tuning in the $d$ band