Spin-orbit torques in strained PtMnSb from first principles

TL;DR

This study uses first-principles calculations to analyze how strain affects spin-orbit torques in PtMnSb, revealing linear strain dependence in field-like SOTs and insensitivity of antidamping SOT to certain strains, with implications for spintronic device design.

Contribution

The paper introduces a comprehensive symmetry-based expansion of SOTs including higher-order terms and compares the effects of different exchange-correlation potentials on these torques.

Findings

Field-like SOTs strongly depend on strain.

Antidamping SOT is less sensitive to strain.

Higher-order terms are less affected by strain and exchange-correlation potential.

Abstract

We compute spin-orbit torques (SOTs) in strained PtMnSb from first principles. We consider both tetragonal strain and shear strain. We find a strong linear dependence of the field-like SOTs on these strains, while the antidamping SOT is only moderately sensitive to shear strain and even insensitive to tetragonal strain. We also study the dependence of the SOT on the magnetization direction. In order to obtain analytical expressions suitable for fitting our numerical \textit{ab-initio} results we derive a general expansion of the SOT in terms of all response tensors that are allowed by crystal symmetry. Our expansion includes also higher-order terms beyond the usually considered lowest order. We find that the dependence on the strain is much smaller for the higher-order terms than for the lowest order terms. In order to judge the sensitivity of the SOT on the exchange correlation potential we compute the SOT in both GGA and LDA. We find that the higher-order terms depend significantly on the exchange-correlation potential, while the lowest order terms are insensitive to it. Since the higher-order terms are small in comparison to the lowest order terms the total SOT is insensitive to the exchange correlation potential in strained PtMnSb.