Study of noise sources in thin film media

The noise behavior of planar isotropic thin-film media is studied by examining magnetization configurations as well as pole-density distributions. Magnetization configurations at the remanent coercive state and in transitions are simulated by a micromagnetic model. The magnetic pole-density distributions are studied for films with and without intergranular exchange coupling. It is found that the magnetic poles form clusters and concentrate mainly near magnetization vortices and flux saddle points. In films with intergranular exchange coupling, large position fluctuations of the magnetization vortices and the flux saddle points results in large fluctuations of the pole-density distributions. The DC-erase noise in the remanent coercive state and the transition noise are higher in an exchange-coupled medium than in a film without intergranular exchange coupling