Maximizing spin–orbit torque efficiency of Ta(O)/Py via modulating oxygen-induced interface orbital hybridization
Liupeng Yang, Yining Fei, Kaiyuan Zhou, Lina Chen, Qingwei Fu, Liyuan Li, Chunjie Yan, Haotian Li, Youwei Du, Ronghua Liu
Abstract
Spin–orbit torques due to interfacial Rashba and spin Hall effects have been widely considered as a potentially more efficient approach than the conventional spin-transfer torque to control the magnetization of ferromagnets. We report a comprehensive study of spin–orbit torque efficiency in Ta(O)/Ni81Fe19 bilayers by tuning low-oxidation of β-phase tantalum and find that the spin Hall angle θDL increases from ∼−0.18 of the pure Ta/Py to the maximum value ∼−0.30 of Ta(O)/Py at 7.8% oxidation. Furthermore, we distinguish the spin–orbit torque efficiency generated by the bulk spin Hall effect and interfacial Rashba effect, respectively, via a series of Ta(O)/Cu(0–2 nm)/Py control experiments. The latter has more than twofold enhancement and is even more significant than the former at the optimum oxidation level. Our results indicate that 65% enhancement of the efficiency should be related to the modulation of the interfacial Rashba-like spin–orbit torque due to oxygen-induced orbital hybridization across the interface. Our results suggest that the modulation of interfacial coupling via oxygen-induced orbital hybridization can be an alternative method to boost the change-spin conversion efficiency.