Permeability and Anisotropy Dispersion of Amorphous Soft Magnetic Films

The frequency dependence of permeability has been calculated for soft magnetic thin films which have a uniaxial anisotropy with both amplitude and angular dispersion. These calculations have been performed for amorphous Co-Nb films, whose anisotropy dispersion has been determined by low-frequency FMR measurements. Comparison of the measured permeability with calculations suggests that the effective uniaxial anisotropy is dispersed more widely and with a smaller amplitude than is indicated by FMR measurements. The magnetization ripple is inferred to be one of the causes of the low value for the effective field.