High electrical resistivity and permeability of soft magnetic granular alloys

The electrical resistivity and magnetic properties were investigated on sputtered CoFeB-O and CoAl-O granular alloy thin films, which are considered to be new-type of magnetic thin film useful in the very high frequency region. A tunnel-hopping conductivity described by exp(/spl alpha/T/sup -1/2/) was observed in films with higher O content. The coefficient /spl alpha/, proportional to the root of tunnel-activation energy, was smaller than that of similar granular systems composed of a mixture of metallic and non-metallic particles. The frequency dependence of the permeabilities in these films was remarkably flat up to high frequencies (/spl sim/50 MHz), although the loss terms were slightly larger than those calculated by the Landau-Lifshitz equation using the observed high resistivities.<
>