Frequency Dependence of Permeability in Fe-Zr-N Film

The effects of the thickness, uniaxial anisotropy field, electrical resistivity and addition of other elements on the frequency dependence of permeability in Fe-Zr-N films were investigated. Film thicknesses were varied up to 8 μm. The purpose of this study was to identify the main origin of the high-frequency loss in thick films in order to allow them to be applied in magnetic heads. The results showed that the main origin of the loss in high-anisotropy film was eddy currents. Although an anisotropy dispersion existed, the permeability at magnetic head-driving frequencies below 30 MHz can be explained using the classical equation for eddy current losses with an effective uniaxial anisotropy field. On the other hand, the permeability of low-anisotropy film disagreed with the results obtained from the classical equation. The effect of anisotropy dispersion must be considered in order to explain the permeability of these low-anisotropy films.