We show that the current-induced torque generated can be significantly enhanced by the oxidation of metals. The oxidation allows efficient generation of the current-induced torques using Cu, a light metal with weak spin-orbit coupling [1]. We also show that the torque efficiency of ferromagnetic-metal/Cu-oxide bilayers can be maximized by a fine tuning of the oxidation level of the Cu layer [2]. The origin of the maximization is attributed to the enhancement of the interface spin-orbit coupling, showing that the bulk spin-orbit coupling of the oxidized Cu layer plays a minor role in the generation of the torque generation by naturally oxidized Cu.
[1] H. An, Y. Kageyama, Y. Kanno, N. Enishi and K. Ando, Nature Communications 7, 13069 (2016).
[2] Y. Kageyama, Y. Tazaki, H. An, T. Harumoto, T. Gao, J. Shi, and K. Ando, Science Advances 5, eaax4278 (2019).
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