Skyrmions are spiral structures observed in thin films of certain magnetic materials (Uchida et al 2006 Science 311 359-61). Of the phases allowed by the crystalline symmetries of these materials (Yi et al 2009 Phys.Rev. B 80 054416), only the hexagonally packed phases (SC h ) have 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 lowtemperature 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.

pacs: 75.30. Kz,64.70.dj,07.05.Tp,75.30.Cr The strength of perpendicular anisotropy is known to drive the spin reorientation in thin magnetic films. Here we consider the effect different order anisotropies have on two phase transitions; the spin reorientation transition and the orientational order transition. We find that the relative magnitude of different order anisotropies can significantly enhance or suppress the degree to which the system reorients. Specifically Monte Carlo simulations reveal significant changes in the cone angle and planar magnetization. In order to facilitate rapid computation we have developed a stream processing technique, suitable for use on GPU systems, for computing the transition probabilities in two dimensional systems with dipole interactions.

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