Chin. Phys. B, 2021, Vol. 30(3): 037503    DOI: 10.1088/1674-1056/abe3f4
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# Enhanced spin-orbit torque efficiency in Pt100-xNix alloy based magnetic bilayer

Congli He(何聪丽)1,†, Qingqiang Chen(陈庆强)1,†, Shipeng Shen(申世鹏)1, Jinwu Wei(魏晋武)2, Hongjun Xu(许洪军)2, Yunchi Zhao(赵云驰)2, Guoqiang Yu(于国强)2, and Shouguo Wang(王守国)1,
1 Institute of Advanced Materials, Beijing Normal University, Beijing 100875, China; 2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Abstract  The binary alloy/ferromagnetic metal heterostructure has drawn extensive attention in the research field of spin-orbit torque (SOT) due to the potential enhancement of SOT efficiency via composition engineering. In this work, the magnetic properties and SOT efficiency in the Pt100-xNix/Ni78Fe22 bilayers were investigated via the spin-torque ferromagnetic resonance (ST-FMR) technique. The effective magnetic anisotropy field and effective damping constant extracted by analyzing the ST-FMR spectra show a weak dependence on the Ni concentration. The effective spin-mixing conductance of $8.40\times 10^14 \Omega ^-1\cdot\rm m^-2$ and the interfacial spin transparency T in of 0.59 were obtained for the sample of Pt70Ni30/NiFe bilayer. More interestingly, the SOT efficiency that is carefully extracted from the angular dependence of ST-FMR spectra shows a nonmonotonic dependence on the Ni concentration, which reaches the maximum at x = 18. The enhancement of the SOT efficiency by alloying the Ni with Pt shows potential in lowering the critical switching current. Moreover, alloying relatively cheaper Ni with Pt may promote to reduce the cost of SOT devices.
Keywords:  spin-orbit torque      magnetic doping      spin-torque ferromagnetic resonance
Published:  22 February 2021
 PACS: 75.47.-m (Magnetotransport phenomena; materials for magnetotransport) 85.75.-d (Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields) 71.70.Ej (Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect)
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 51901025 and 51625101), the Fundamental Research Funds for the Central Universities, China (Grant No. 310421101), and the Beijing Natural Science Foundation, China (Grant No. Z190007).
Corresponding Authors:  These authors contributed equally. §Corresponding author. E-mail: sgwang@bnu.edu.cn