Exchange-anisotropy-induced intrinsic distortion, structural transition, and rotational transition in skyrmion crystals

作者：Xuejin Wan, Yangfan Hu, Biao Wang · 发表于：Physical review. B./Physical review. B · 年份：2018 · DOI：10.1103/physrevb.98.174427 · 被引用次数：9 · 研究领域：Magnetic properties of thin films、Magnetic and transport properties of perovskites and related materials、Physics of Superconductivity and Magnetism

Magnetic skyrmions are topologically protected noncollinear spin textures. Their condensed state, called skyrmion crystal phase (SkX), is usually presumed to be hexagonally symmetric as observed in most helimagnets. However, careful study of the experimental results indicates the existence of intrinsic anisotropy of SkX, reflected by breaking of SkX hexagonal symmetry, direction-dependent properties of SkX, and even the appearance of novel emergent crystalline states. Here, we systematically study the effects of exchange anisotropy on Bloch-type SkX in cubic helimagnets and provide a possible explanation to the phenomena mentioned above. By energy minimization, we find that exchange anisotropy causes intrinsic distortion of SkX. As the magnitude of exchange anisotropy changes, a triangular-square transition occurs, with two possible transition paths for different choices of anisotropy parameters. We also reproduce the ${30}^{\ensuremath{\circ}}$ rotational transition of SkX.