Monte Carlo studies of the phases and phase diagram of quasi 2D Skyrmion systems

We present results for large-scale Monte Carlo simulations of the field-temperature phase diagram of thin-film chiral magnets with ferromagnetic exchange and Dzyaloshinskii-Moriya interaction. Using spin structure factors, skyrmion density structure factors, magnetization and specific heat, we show that there are five interesting regions of the phase diagram: (1) a skyrmion solid phase, (2) a skyrmion liquid regime, (3) a helical phase, (4) a fluctuating helical regime, and (5) a field-polarized regime. Using orientational order parameters we identify the phase boundaries for the skyrmion melting transition and the helical melting transition. We also investigate the phase diagram as a function of film thickness L, showing how that the interlayer correlations and the maximum transition temperature for the skyrmion solid evolves as a function of L/L_D, where L_D is the helical pitch length.