Phase transitions between helices, vortices, and hedgehogs driven by spatial anisotropy in chiral magnets

TL;DR

This paper investigates how spatial anisotropy influences topological spin textures in chiral magnets, revealing the transformation of hedgehog lattices into lower-dimensional structures like vortices and helices, with implications for controlling magnetic properties.

Contribution

The study provides a theoretical analysis of anisotropy effects on topological spin textures, demonstrating their deformation and transformation in chiral magnetic models.

Findings

Hedgehog lattices deform into vortices and helices under anisotropy.

Topological properties change with the real-space positions of monopoles.

Anisotropy can be used to control spin textures in chiral materials.

Abstract

Superpositions of spin helices can yield topological spin textures, such as two-dimensional vortices and skyrmions, and three-dimensional hedgehogs. Their topological nature and spatial dimensionality depend on the number and relative directions of the constituent helices. This allows mutual transformation between the topological spin textures by controlling the spatial anisotropy. Here we theoretically study the effect of anisotropy in the magnetic interactions for an effective spin model for chiral magnetic metals. By variational calculations for both cases with triple and quadruple superpositions, we find that the hedgehog lattices, which are stable in the isotropic case, are deformed by the anisotropy, and eventually changed into other spin textures with reduced dimension, such as helices and vortices. We also clarify the changes of topological properties by tracing the real-space positions of magnetic monopoles and antimonopoles as well as the emergent magnetic field generated by the noncoplanar spin textures. Our results suggest possible control of the topological spin textures, e.g., by uniaxial pressure and chemical substitution in chiral materials.