Current-induced spin-orbit torques (SOTs) are of interest for fast and energy-efficient manipulation of magnetic order in spintronic devices. To be deterministic, however, switching of perpendicularly magnetized materials by SOT requires a mechanism for in-plane symmetry breaking. Existing methods to do so involve the application of an in-plane bias magnetic field, or incorporation of in-plane structural asymmetry in the device, both of which can be difficult to implement in practical applications. Here, we reported bias-field-free SOT switching in a single perpendicular CoTb layer with an engineered vertical composition gradient. The vertical structural inversion asymmetry induces strong intrinsic SOTs and a gradient-driven Dzyaloshinskii-Moriya interaction (g-DMI), which breaks the in-plane symmetry during the switching process. Micromagnetic simulations are in agreement with experimental results, and elucidate the role of g-DMI in the deterministic switching. This bias-field-free switching scheme for perpendicular ferrimagnets with g-DMI provides a strategy for efficient and compact SOT device design.
@article{arxiv.2101.08518,
title = {Field-free spin-orbit torque-induced switching of perpendicular magnetization in a ferrimagnetic layer with vertical composition gradient},
author = {Zhenyi Zheng and Yue Zhang and Victor Lopez-Dominguez and Luis Sánchez-Tejerina and Jiacheng Shi and Xueqiang Feng and Lei Chen and Zilu Wang and Zhizhong Zhang and Kun Zhang and Bin Hong and Yong Xu and Youguang Zhang and Mario Carpentieri and Albert Fert and Giovanni Finocchio and Weisheng Zhao and Pedram Khalili Amiri},
journal= {arXiv preprint arXiv:2101.08518},
year = {2021}
}