Chiral skyrmion states in non-centrosymmetric magnets

TL;DR

This paper provides a detailed numerical analysis of chiral skyrmion lattices in non-centrosymmetric cubic helimagnets, extending previous approximate models and describing their evolution under various external conditions.

Contribution

It offers a rigorous numerical solution for hexagonal skyrmion lattices, improving upon earlier approximate methods and broadening understanding of their stability and transformation.

Findings

Numerical solutions confirm the stability of skyrmion lattices.

Skyrmion lattice evolution is described under magnetic field and anisotropy.

Extended theoretical framework beyond circular cell approximation.

Abstract

Chiral skyrmion states exist in non - centrosymmetric magnetic crystals as a consequence of the asymmetric exchange Dzyaloshinskii-Moriya interactions that destroy the homogeneous magnetic state and generally lead to twisted incommensurate magnetic spin-structures. Recently, skyrmion lattices and free skyrmions in magnetic layers of the chiral helimagnets with the noncentrosymmetric cubic B20 crystal structure have been observed. The stabilization of these states and their transformation properties impressively illustrate the theoretically predicted solitonic nature of these chiral two-dimensionally localized spin-states. This paper is mainly devoted to numerically rigorous solutions of hexagonal skyrmion lattices for cubic helimagnets. It justifies and extends previous approximate solutions that used a circular cell approximation (CCA) for the calculation of the free energy of skyrmion lattices. The theoretical results of the present paper provide a comprehensive description of skyrmion lattice evolution in an applied magnetic field and/or in the presence of uniaxial, cubic, and exchange anisotropy. The low-temperature phenomenological theory with fixed modulus of magnetization, M=const, is applied to the magnetic states in chiral magnets.