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.