Bubble and Skyrmion Crystals in Frustrated Magnets with Easy-Axis Anisotropy

TL;DR

This paper investigates how lattice and easy-axis anisotropies in frustrated magnets promote complex magnetic structures, revealing conditions for skyrmion and bubble crystal formations influenced by anisotropy strength and magnetic fields.

Contribution

It clarifies the role of anisotropy in stabilizing multiple-Q magnetic structures, including skyrmion and bubble crystals, in frustrated magnets with multiple exchange minima.

Findings

Moderate anisotropy induces skyrmion crystals under magnetic fields.

Increasing anisotropy transforms skyrmion crystals into bubble crystals.

Bubble crystals show a temperature-dependent wave-vector with devil's staircase behavior.

Abstract

We clarify the conditions for the emergence of multiple-${\bf Q}$ structures out of lattice and easy-axis spin anisotropy in frustrated magnets. By considering magnets whose exchange interaction has multiple global minima in momentum space, we find that both types of anisotropy stabilize triple-${\bf Q}$ orderings. Moderate anisotropy leads to a magnetic field-induced skyrmion crystal, which evolves into a bubble crystal for increasing spatial or spin anisotropy. The bubble crystal exhibits a quasi-continuous (devil's staircase) temperature dependent ordering wave-vector, characteristic of the competition between frustrated exchange and strong easy-axis anisotropy.