Theory of the skyrmion, meron, antiskyrmion, and antimeron in chiral magnets

Abstract

We find closed-form solution of the Euler equation for a chiral magnet in terms of a skyrmion or a meron depending on the relative strengths of magnetic anisotropy and magnetic field. We show that the relevant length scales for these solutions primarily depend on the strengths of Dzyaloshinskii-Moriya interaction through its ratios, respectively, with magnetic field and magnetic anisotropy. We thus unambiguously determine the parameter dependencies on the radius of the topological structures particularly of the skyrmions, showing an excellent agreement with experiments and first-principles studies. An anisotropic Dzyaloshinskii-Moriya interaction suitable for thin films made with Cnv symmetric materials is found to stabilize antiskyrmion and antimeron, which are prototypical for D2d symmetric systems, depending on the degree of anisotropy. Based on these solutions, we obtain a phase diagram by comparing the energies of various collinear and noncollinear competing phases.