Symmetry-breaking effects on spin-orbit torque switching in ferromagnetic semiconductors with perpendicular magnetic anisotropy

TL;DR

This paper investigates how symmetry-breaking influences spin-orbit torque switching in ferromagnetic semiconductors with perpendicular magnetic anisotropy, revealing mechanisms for field-free switching and implications for spintronics.

Contribution

It identifies and analyzes various symmetry-breaking factors that enable field-free SOT switching in ferromagnetic semiconductors, providing new insights for optimizing spintronic device performance.

Findings

Bias field misalignment distorts SOT hysteresis.

Intrinsic symmetry-breaking enables field-free SOT switching.

Distinct FF-SOT characteristics include hysteresis shifts and switching ratios.

Abstract

This study explores the mechanisms of spin-orbit torque (SOT) switching in ferromagnetic semiconductors (FMS) with perpendicular magnetic anisotropy (PMA), emphasizing the impact of symmetry-breaking. Using micromagnetic simulations based on the Landau-Lifshitz-Gilbert (LLG) equation, we examine several symmetry-breaking factors, including bias field misalignment, interlayer exchange coupling, out-of-plane spin polarization, and tilted magnetic anisotropy. The results reveal that bias field misalignment relative to the film plane significantly distorts the SOT switching hysteresis. Additionally, intrinsic symmetry-breaking effects, such as internal coupling fields, out-of-plane spin polarization, and tilted anisotropy, facilitate field-free SOT (FF-SOT) switching without external bias fields. Each type of FF-SOT switching exhibits distinct characteristics, including hysteresis shifts, switching ratios, and saturated magnetization. This work emphasizes the role of symmetry-breaking in FF-SOT switching and offers fundamental information for interpreting FF-SOT switching observed from FMS films in experiments, contributing to the optimization of SOT efficiency and the advancement of spintronics technologies.