Rectangular and square skyrmion crystals on a centrosymmetric square lattice with easy-axis anisotropy

Abstract

We investigate the instability toward a skyrmion crystal under an in-plane magnetic field in centrosymmetric tetragonal magnets. By performing the simulated annealing for a spin model on the square lattice, we find that the interplay among the easy-plane two-spin anisotropic interaction, positive biquadratic interaction, and high-harmonic wave-vector interaction plays an important role in stabilizing the skyrmion crystal in the in-plane external magnetic field. The obtained skyrmion crystal consists of a pair of vortex and antivortex with opposite polarization in terms of the out-ofplane spin component. We also show that various multiple-Q states emerge depending on the model parameters. Our results indicate the possibility of topological spin textures in centrosymmetric tetragonal magnets with easy-plane magnetic anisotropy when the ground-state spin configuration at zero field is characterized by a single-Q in-plane cycloidal spiral state.

Orthorhombic distortion and rectangular skyrmion crystal in a centrosymmetric tetragonal host

“…that the effect of magnetic frustration in momentum space is large, which becomes the origin of two types of the SkXs (S-SkX and R-SkX) [59,60]. Indeed, for this set of model parameters, it was revealed that the above two SkXs appear in the presence of an external magnetic field H in the second term in equation ( 1) [52].…”

Topological magnons in a non-coplanar magnetic order on the triangular lattice

“…This is just the tip of the iceberg of topological non-trivial spin textures [39]. On the one hand, it has been proved that the skyrmion can also appear in the centrosymmetric magnets as a result of other interactions [49][50][51][52][53][54][55][56][57][58][59][60], such as dipolar interaction [49,50], the single-ion anisotropy [51][52][53][54][55][56][57][58] or the bond-dependent interactions [54,61]. On the other hand, beyond the skyrmion, there are many magnetic quasi-particles coming into the sight of researchers in recent years [39,62,63].…”

Square skyrmion crystal in centrosymmetric systems with locally inversion-asymmetric layers

“…In fact, the stabilization of the centrosymmetric square SkX has been achieved by considering the further effect of the bonddependent anisotropic exchange interaction or the dipolar interaction in addition to the frustrated exchange interaction in insulating magnets [89,90] and the multiple-spin interaction in magnetic metals [87,[146][147][148][149], which reproduces the multiple-Q instabilities observed in GdRu 2 Si 2 [103][104][105]. Besides, the scenario based on the competing interactions in momentum space has recently been proposed, which might explain the multiple SkX phases including the square SkX in EuAl 4 [109,150,151].…”