Skyrmions as quasiparticles: Free energy and entropy

The free energy and the entropy of magnetic skyrmions with respect to collinear state are calculated for a (Pt$_{0.95}$Ir$_{0.05}$)/Fe bilayer on Pd(111) via atomistic spin model simulations. simulations carried out starting from very low temperatures where skyrmion number is conserved up range constantly created destroyed by thermal fluctuations, highlighting their quasiparticle nature. higher at temperature leads reduced energy, such that become energetically preferred over due entropic stabilization as predicted linear spin-wave theory. Going beyond approximation, sign change shown occur in well elevated temperature.