The stability of 3D skyrmions under mechanical stress studied via Monte Carlo calculations

TL;DR

This study uses Monte Carlo simulations to analyze how uniaxial mechanical stresses influence the stability of 3D skyrmions in chiral magnetic materials, revealing the role of DMI anisotropy in their stability.

Contribution

It introduces a Finsler geometry modeling approach with strain degrees of freedom to explain skyrmion stability changes under mechanical stress.

Findings

Skyrmion stability increases with tensile strain parallel to magnetic field.

Skyrmion stability decreases with compressive stress perpendicular to magnetic field.

DMI anisotropy explains experimentally observed stability and instability of skyrmions.

Abstract

Using Monte Carlo (MC) simulations, we study the skyrmion stability/instability as a response to uniaxial mechanical stresses. Skyrmions emerge in chiral magnetic materials as a stable spin configuration under external magnetic field $\vec{B}$ with the competition of ferromagnetic interaction and Dzyaloshinskii-Moriya interaction (DMI) at low temperature $T$. Skyrmion configurations are also known to be stable (unstable) under a compressive stress applied parallel (perpendicular) to $\vec{B}$. To understand the origin of such experimentally confirmed stability/instability, we use the Finsler geometry modeling technique with a new degree of freedom for strains, which plays an essential role in DMI being anisotropic. We find from MC data that the area of the skyrmion state on the $B$-$T$ phase diagram increases (decreases) depending on the direction of applied stresses, in agreement with reported experimental results. This change in the area of the skyrmion state indicates that skyrmions become more (less) stable if the tensile strain direction is parallel (perpendicular) to $\vec{B}$. From the numerical data in this paper, we find that the so-called magneto-elastic effect is suitably implemented in the effective DMI theory with the strain degree of freedom without complex magneto-elastic coupling terms for chiral magnetic materials. This result confirms that experimentally-observed skyrmion stability and instability are caused by DMI anisotropy.