Magnetic, electrical and structural properties of granular [FeCoB/(SiO2)]xn thin films

The granular metal-insulator films are composite materials consisting of metallic nanograins embedded in an insulating matrix. The ferromagnetic metal-insulator thin films with very high electrical resistivity are an excellent candidate for high permeability cores in thin film inductors which operate at high frequencies. A source of losses are eddy currents in the magnetic layers. A possible way to reduce these losses is to fabricate the magnetic/dielectric multilayers. This paper reports some results concerning the influence of the FeCoB and SiO2 layers composition and annealing temperature on the resistive, magnetic and microstructural properties of [FeCoB/(SiO2)] x n multilayer thin films. As compared to the well known FeCoB alloys, widely used in the electromagnetic micro-devices which can operate at high frequencies, the [FeCoB/(SiO2)] x n (ngreater than or equal to30) thin films exhibit high resistivity over 8x10(-3) mOmega.m while superior soft magnetic properties specific for FeCoB thin films are maintained. The [FeCoB/(SiO2)] x 60 thin films after annealing at 300degreesC show good resistive and magnetic properties of the resistivity rhocongruent to49 mOmega m, saturation magnetization Mscongruent to149 emu/g and coercive field Hccongruent to7 Oe.