Skyrmion crystal phase on a magnetic domain wall in chiral magnets

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.