Computer simulation of thermal activation volume in HDD media

The thermal activation volume in hard-disk media was investigated through micro-magnetic simulation. It was found that the activation volume should be obtained by using the time-dependent irreversible magnetization (viscosity). The method using the total magnetization including the reversible magnetization leads to a wrong dependence of the activation volume on the field. The relationship between the switching volume in a hard-disk medium and the activation volume is described as a function of the exponent of the dynamic coercivity, the switching field, and the anisotropy field.