Micromagnetics of hysteresis loops in CGC perpendicular media

Magnetization reversal mechanisms in coupled granular/continuous perpendicular media are investigated using a three-dimensional micromagnetic model. Hysteresis loops for media with reduced exchange coupling between the continuous and granular layers are found to reverse via a three-stage reversal process. Reversal within soft grains in the granular layer is found to reduce the nucleation field by destabilizing the continuous layer, while hard grains that do not reverse when the continuous layer switches determine the saturation field H_s.