Micromagnetic Simulation of Thermal Activation Volume in Perpendicular Recording Media With Dispersions of Grain Size

The process of thermal switching and thermal activation volume of perpendicular recording media with dispersions of grain size have been analyzed using micromagnetic simulation with Voronoi lattice model. It was found that in media with smaller inter-grain exchange coupling w, almost all grains switch thermally alone, and the average activation volume langV_acrang does not depend on the applied DC reverse field significantly. While, in media with larger w, several neighboring grains switched simultaneously and langV_acrang increased with increasing reverse field, but not so much. It was also found that langV_acrang increased slightly with w until w reached some critical value, beyond which langV_acrang increased remarkably with w