Melting of hexagonal Skyrmion states in chiral magnets

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.