High-Frequency Properties and Thickness-Dependent Damping Factor of ${\rm FeCo}{\hbox{–}}{\rm SiO}_{2}$ Thin Films

Abstract

Soft magnetic nanogranular Fe70Co30-SiO2 thin films were fabricated on Si substrates using radio frequency (rf) magnetron sputtering in an argon ambient. The electrical, magnetic and high-frequency properties of these thin films were studied in details. SiO2 chips were placed in the erosion race-track of the alloy Fe70Co30 (at.%) target and change the number of chips result in the different film composition. The optimal films with desired properties of low coercivity, Hc ~ 2.5 Oe, high saturation magnetization, 4π Ms ~ 11.6 kGs and high electrical resistivity ρ ~ 1600 μΩcm were obtained. Permeability spectra measured shows that its natural ferromagnetic resonant (FMR) frequency (fr) and initial permeability were about 4.05 GHz and 120, respectively. The tested results shown that the film thickness had an important effect on films properties, it can convenient adjust the fr and damping factor of films. With the increase of film thickness from 50 nm to 1200 nm, the fr of films ranged from 2.86 GHz to 4.05 GHz. The excellent soft magnetic properties were ascribed to exchange coupling among magnetic particles.