Nanogranular CoFe-Yttrium-Doped Zirconia Films for Noise Suppressor

Magnetic nanogranular CoFe-yttrium-doped zirconia (CoFe-YSZ) films have been deposited by radio-frequency magnetron cosputtering. By simply adjusting the thickness of films, the imaginary permeability spectrum of CoFe-YSZ films changed from a resonance-type permeability spectra to a relaxation-type permeability spectra. Based on this phenomenon, nanogranular CoFe-YSZ films with various thicknesses were deposited. The characteristics of the electromagnetic noise suppression have been evaluated using an integrated coplanar waveguide transmission line. The CoFe-YSZ film of 821 nm shows a very wide resonance peak with the full-width at half-maximum of 2.8 GHz. The absorption attenuation amplitude reaches -8.3 dB at the resonance frequency, which is better than -6.2 dB for the frequency above 3.5 GHz. The physical origin of these influences was suggested to be the structure and composition changes of the films. In addition, the variations of ferromagnetic resonance peak broadness of the imaginary part and damping factor were also discussed as functions of film thickness.