Direction-Dependent Stability of skyrmion lattice in helimagnets induced by Exchange Anisotropy

TL;DR

This paper investigates how exchange anisotropy influences the stability of skyrmion lattices in helimagnets, revealing that combined effects of anisotropy and thermal fluctuations determine phase stability.

Contribution

It introduces a phenomenological mean-field model incorporating exchange anisotropy to explain the direction-dependent stability of skyrmion lattices in MnSi.

Findings

Exchange anisotropy causes direction-dependent phase stability.

Negative exchange anisotropy and thermal fluctuations jointly stabilize skyrmion lattices.

Fourier representation affects equilibrium properties of skyrmion phases.

Abstract

Exchange anisotropy provides a direction dependent mechanism for the stability of the skyrmion lattice phase in noncentrosymmetric bulk chiral magnets. Based on the Fourier representation of the skyrmion lattice, we explain the direction dependence of the temperature-magnetic field phase diagram for bulk MnSi through a phenomenological mean-field model incorporating exchange anisotropy. Through quantitative comparison with experimental results, we clarify that the stability of the skyrmion lattice phase in bulk MnSi is determined by a combined effect of negative exchange anisotropy and thermal fluctuation. The effect of exchange anisotropy and the order of Fourier representation on the equilibrium properties of the skyrmion lattice is discussed in detail.