Anisotropic skyrmion crystal on a centrosymmetric square lattice under an in-plane magnetic field

TL;DR

This study demonstrates the stabilization of anisotropic skyrmion crystals in centrosymmetric square lattice magnets under in-plane magnetic fields, highlighting the roles of anisotropic interactions and high-harmonic couplings.

Contribution

It reveals the conditions and interactions that stabilize skyrmion crystals in centrosymmetric tetragonal magnets with easy-plane anisotropy, a novel insight into topological spin textures.

Findings

Skyrmion crystals consist of vortex-antivortex pairs with opposite out-of-plane polarization.

Multiple-Q states emerge depending on model parameters.

Skyrmion stabilization is linked to specific anisotropic and high-harmonic interactions.

Abstract

We investigate the instability toward a skyrmion crystal under an in-plane magnetic field in centrosymmetric tetragonal magnets. By performing the simulated annealing for a spin model on the square lattice, we find that the interplay among the easy-plane two-spin anisotropic interaction, positive biquadratic interaction, and high-harmonic wave-vector interaction plays an important role in stabilizing the skyrmion crystal in the in-plane external magnetic field. The obtained skyrmion crystal consists of a pair of vortex and antivortex with opposite polarization in terms of the out-of-plane spin component. We also show that various multiple-$Q$ states emerge depending on the model parameters. Our results indicate the possibility of topological spin textures in centrosymmetric tetragonal magnets with easy-plane magnetic anisotropy when the ground-state spin configuration at zero field is characterized by a single-$Q$ in-plane cycloidal spiral state.