Finsler geometry modeling and Monte Carlo study of skyrmion shape deformation by uniaxial stress

TL;DR

This paper introduces a Finsler geometry-based modeling approach to study how uniaxial stress causes shape deformation in magnetic skyrmions, revealing the anisotropic effects on magnetic interactions.

Contribution

It develops two novel Finsler geometry models to analyze the anisotropic deformation of skyrmions under mechanical stress, aligning with experimental observations.

Findings

Finsler geometry models agree with experimental skyrmion deformation data.

Distinct responses of helical spin orders under lattice deformation.

Differentiates the deformation effects on FMI and DMI interactions.

Abstract

Skyrmions in chiral magnetic materials are topologically stable and energetically balanced spin configurations appearing under the presence of ferromagnetic interaction (FMI) and Dzyaloshinskii-Moriya interaction (DMI). Much of the current interest has focused on the effects of magneto-elastic coupling on these interactions under mechanical stimuli, such as uniaxial stresses for future applications in spintronics devices. Recent studies suggest that skyrmion shape deformations in thin films are attributed to an anisotropy in the coefficient of DMI, such that $D_{x}\!\not=\!D_{y}$, which makes the ratio $\lambda/D$ anistropic, where the coefficient of FMI $\lambda$ is isotropic. It is also possible that $\lambda_{x}\!\not=\!\lambda_{y}$ while $D$ is isotropic for $\lambda/D$ to be anisotropic. In this paper, we study this problem using a new modeling technique constructed based on Finsler geometry (FG). Two possible FG models are examined: In the first (second) model, the FG modeling prescription is applied to the FMI (DMI) Hamiltonian. We find that these two different FG models' results are consistent with the reported experimental data for skyrmion deformation. We also study responses of helical spin orders under lattice deformations corresponding to uniaxial extension/compression and find a clear difference between these two models in the stripe phase, elucidating which interaction of FMI and DMI is deformed to be anisotropic by uniaxial stresses.