Domain dynamics of magnetic films with perpendicular anisotropy

Abstract

We study the magnetic properties of nanoscale magnetic films with large perpendicular anisotropy comparing polarization-microscopy measurements on ${\mathrm{Co}}_{28}{\mathrm{Pt}}_{72}$-alloy samples based on the magneto-optical Kerr effect with Monte Carlo simulations of a corresponding micromagnetic model. In our model the magnetic film is described in terms of single-domain magnetic grains interacting via exchange as well as via dipolar forces. Additionally, the model contains an energy barrier which has to be overcome in order to reverse a single cell and a coupling to an external magnetic field. Disorder is taken into account. We focus on the understanding of the dynamics especially the temperature and field dependence of the magnetization reversal process. The experimental and simulation results for hysteresis, the reversal mechanism, domain configurations during the reversal, and the time dependence of the magnetization are in very good qualitative agreement. The results for the field and temperature dependence of the domain wall velocity suggest that for thin films the hysteresis can be described as a depinning transition of the domain walls rounded by thermal activation for finite temperatures.