Relation between magnetic cluster size and thermal switching size in HDD media

Summary form only given. As the recording density of hard-disk drives becomes higher, it becomes more important to retain thermal stability and reduce media noise at the same time. The media noise is thought to depend on magnetic cluster size D/sub cluster/. However, the relation between D/sub cluster/ and thermal switching size D/sub switch/ is not clear. In this study, D/sub cluster/ and D/sub switch/ have been analyzed by using micro-magnetic simulation. A 32/spl times/32 array of single-domain grains with the same grain size D was used to simulate a longitudinal recording medium. The easy axis of each grain was randomly distributed in the film plane. The time evolution of the magnetization of the grains was calculated by solving the Langevin equation. The average diameter of the unit of thermal switching, in which the magnetizations switch simultaneously, was defined as D/sub switch/.