Thickness Dependence of Induced Magnetic Anisotropy in Evaporated Permalloy Films

The uniaxial magnetic anisotropy (Ku) of evaporated Permalloy films of different thicknesses was measured. For thinner films, measurements relied on the magnetoresistive (¿R) effect. Although there was considerable scattering in the results, Ku tended to decrease as films were made thinner than 500 Å, and disappeared at around 100 to 300 Å. This decrease is thought to be related to the island structure of extremely thin films, in which case the anisotropy finally disappears in fine crystal grains of size arotund 100 Å.