Spin-orbit torques in bulk collinear antiferromagnets:complete classifications and the induced spin dynamics

TL;DR

This paper classifies spin-orbit torques in bulk collinear antiferromagnets based on symmetry, investigates their effects on Neel vector dynamics, and demonstrates potential for electric control of antiferromagnetic memory devices.

Contribution

It provides a complete symmetry-based classification of SOTs in collinear AFMs and explores their impact on spin dynamics and memory applications.

Findings

Six types of SOTs classified by symmetry.

Deterministic Neel vector switching driven by field-like torques.

Electric writing and reading of antiferromagnetic domains demonstrated.

Abstract

Electric field induced spin-orbit torques are the crucial mechanism for electric regulations of antiferromagnetic order. However, the spin-orbit torques in antiferromagnets and the induced spin dynamics remain largely unexplored. In this work, the full classifications of SOTs in bulk collinear AFMs have been achieved based on magnetic point group. Dependent on the symmetries connecting the opposite spin sublattices, the SOTs are classified into six distinct types. Among them, the SOTs and the induced Neel vector dynamics in three representative AFMs have been investigated, where the spin sublattices are connected by fractional translation, spatial inversion, and neither by translation nor inversion symmetry respectively. The SOTs on spin sublattices have been calculated by first-principles calculations based on Kubo linear response theory, and then the induced spin dynamics are simulated by LLG equations. In typical PT symmetric AFM and the inversion symmetry breaking altermagnet, the simulations indicate that the deterministic switching of Neel vectors can be driven by field like torques. What's more, the fully electric writing of multiple antiferromagnetic domains into single domain state with preset Neel vector direction and 180 deterministic switching may also be realized. Our work may shed light on the current control of antiferromagnetic orders in collinear AFMs. Especially, for inversion symmetry breaking altermagnet, the electric writing and reading of Neel vector are highly desirable for antiferromagnetic memory applications.