Melting of hexagonal Skyrmion states in chiral magnets

TL;DR

This paper investigates the melting process of hexagonal Skyrmion phases in chiral magnets through Monte Carlo simulations, revealing that profile changes, not destruction, cause chiral charge reduction at low temperatures, and symmetry loss involves elongated Skyrmions.

Contribution

It introduces a morphological measure to analyze Skyrmion melting and distinguishes profile changes from destruction, providing new insights into phase transitions in chiral magnets.

Findings

Low temperature chiral charge reduction linked to Skyrmion profile changes.

High temperature loss of sixfold symmetry due to elongated Skyrmions.

Morphological measures offer new insights into Skyrmion phase transitions.

Abstract

Skyrmions are spiral structures observed in thin films of certain magnetic materials (10.1126/science.1120639). Of the phases allowed by the crystalline symmetries of these materials(10.1103/PhysRevB.80.054416) only the hexagonally packed phases (SC_h) has been observed. Here the melting of the $SC_h$ phase is investigated using Monte Carlo simulations. In addition to the usual measure of Skyrmion density chiral charge, a morphological measure is considered. In doing so it is shown that the low temperature reduction in chiral charge is associated with a change in Skyrmion profiles rather than Skyrmion destruction. At higher temperatures the loss of six fold symmetry is associated with the appearance of elongated Skyrmions that disrupt the hexagonal packing.