Novel noise model of a perpendicular magnetic recording medium

To explain the origin of noise in a perpendicular magnetic recording medium, the surface-nucleation model which assumes weak anisotropy on the surface layers is utilized. The model shows that DC-erased noise results from tilting magnetization in the film. The tilting angle is increased by the existence of weak anisotropy on the surface layers. The surface layers with weak anisotropy trigger the magnetization reversal of the whole film and enhance thermal fluctuations. As a result, coercivity at a finite temperature decreases dramatically. It is concluded that control the magnetic properties ore the medium surface is very important in order to attain low noise and stability against thermal fluctuation.