Compass-anisotropy-modulated helical states and skyrmion crystals in chiral magnets

The compass-type anisotropy appears naturally in chiral magnets with strong spin-orbit coupling. In this work, we investigate the critical roles of compass anisotropy in modulating various spin textures of chiral magnets, by Monte Carlo simulations. The simulated results reveal a gradual helical reorientation and varying symmetry of skyrmion crystal structures as a function of compass anisotropy. Furthermore, an extended continuum spin model with the lattice discretization anisotropy is proposed to interpret the dependences of helical and skyrmion crystal structures on the compass anisotropy. It is demonstrated that specific helical propagating directions are favored by the high-order lattice anisotropy arising from spin interactions in discretized lattice. Besides that, some threshold values for the helical structures are identified by analytical approach.