Uniaxial anisotropy field and crystalline structures of (CoFe)-(SiO2) magnetic thin film for operating in the GHz frequency

A (CoFe)-(SiO2) magnetic thin film core containing a bcc Co-Fe crystal phase with high saturation magnetization and an amorphous SiO2 phase was fabricated on glass substrates by using synchronous triple-RF magnetron sputtering. The magnetic properties and crystalline structure of the films were investigated in the development of soft magnetic materials operated in the GHz range. The film exhibited a high magnetic resonance frequency (FMR) more than 4 GHz reflecting its large uniaxial anisotropy field Hk of 200 Oe, and a large saturation magnetization 4πMs of 14.5 kG and an electrical resistivity ρ of 1000 μΩ cm. It was found that amorphous SiO2 increased the anisotropy field to 100-200 Oe and that the magnetic properties were associated with changes in the nano-crystalline structure, crystallite sizes and crystallite orientation. The results indicate that (CoFe)-(SiO2) films have potential for use in magnetic cores and inductors operating at GHz frequencies.