Skyrmion crystal phase on a magnetic domain wall in chiral magnets

TL;DR

This paper investigates the phase diagram of magnetic domain walls in chiral magnets, revealing a skyrmion crystal phase and developing an analytical model that aligns well with numerical results but misses some topological details.

Contribution

It introduces a domain-wall theory based on a chiral double sine-Gordon model to analytically reproduce the phase diagram of skyrmion phases in chiral magnetic domain walls.

Findings

Identification of a chiral soliton lattice phase on the domain wall.

Good agreement between numerical and analytical phase diagrams.

Numerical solutions show topological charge decomposition not captured by the effective theory.

Abstract

We study a magnetic domain wall in the ferromagnetic phase in chiral magnets in two dimensions with an in-plane easy-axis anisotropy and an out-of-plane Zeeman magnetic field, and find a chiral soliton lattice (spiral) phase beside a ferromagnetic phase inside the domain line, where the former represents a domain-wall skyrmion crystal from the bulk point of view. We first determine the phase diagram on the domain wall by numerically constructing domain-wall solutions. We then analytically reproduce the phase diagram in a domain-wall theory (a chiral double sine-Gordon model) that we construct within the moduli approximation by treating the Zeeman magnetic field perturbatively. While we find good agreements between the phase diagrams of the numerical and effective theory methods, the numerical solution exhibits a decomposition of the topological charge into a bimeron which cannot be captured by the effective theory.