Model for reversal dynamics of ultrathin ferromagnetic films

We propose a phenomenological model for the dynamic magnetization reversal of epitaxial ultrathin ferromagnetic films with uniaxial in-plane anisotropy. The model assumes that the reversal proceeds via the nucleation of small reversed domains and subsequent domain wall propagation, and that the domain wall velocity depends linearly on the applied magnetic field strength. Two regimes in the dynamic coercive field (H-c*) versus applied field sweep rate [In(DeltaH/Deltat)] data are found in good agreement with experiments. For ultrathin films, the mobility of the domain wall (mu) is found to vary with the thickness of the film (t) according to a power law.