FeNiSiO/SiO₂ multi-layer granular magnetic films with high-resistivity

Abstract

The resistivity and high-frequency permeability of FeNiSiO/SiO₂ multilayer granular magnetic films have been investigated to fabricate a magnetic film with high resistivity suitable for high-frequency micromagnetic devices. High resistivity is obtained by improving the electrical insulation of SiO₂ associated with high-temperature deposition and concurrently by optimizing the microstructure, for example, the grain size of granular Fe-Ni metals and the thickness of SiO₂ layers, which are independently controllable by an alternate sputtering deposition of FeNiSiO granular and SiO₂. The high-frequency permeability are strongly affected by the Fe-Ni grain size as well as the Ni content, due to the influence of super-paramagnetism; the composition of the Fe-Ni grains primarily determines an anisotropy magnetic field (H_k), which is competitive with super-paramagnetism and is a key parameter that affects the high-frequency permeability. The permeability obtained in FeNiSiO/SiO₂ films with a resistivity of 1.1 Ωcm is 460 at 100 MHz.