Influence of multiple magnetic phases on the extrinsic damping of FeCo-SiO2 soft magnetic films

In order to investigate the high-frequency damping properties of the ferromagnetic film for the electromagnetic shielding applications, a series of (FeCo)(2x)/(Fe)(x)/(SiO2)(1-3x) nanogranular films with various volume fractions (x) were fabricated by alternate triple-target magnetron sputtering. The (FeCo)(0.50)/Fe-0.25/(SiO2)(0.25) film shows excellent soft magnetic properties (4 pi M-s similar to 1.48 T, H-ce similar to 4.3 Oe, rho similar to 4.3 mu m). In both ferromagnetic resonance (FMR) and frequency-dependent permeability spectra measurements, two resonance peaks of the permeability for this film are obtained, which can be attributed to the complicated magnetic structure of FeCo and Fe phases in the film. This multiphase system makes an additional contribution to the extrinsic damping. As a result, the higher natural resonance frequency f for the film is up to 2.75 GHz with full width at half maximum of about 2.5 GHz for the imaginary part mu(); meanwhile, the real part mu(/) is as high as 650 while f < 1.3 GHz. These films could be novel candidates for the electromagnetic shielding applications.