Influence of the magnetic field annealing on the extrinsic damping of FeCoB soft magnetic films

In order to investigate the high-frequency damping properties of the ferromagnetic film for the electromagnetic shielding applications, FeCoB films with the thickness of 200 nm were fabricated by the rf magnetron sputtering and subsequently annealed with a static in-plane magnetic field of 2000 Oe under a series of temperatures. The annealed films exhibit excellent soft magnetic and microwave loss properties. The local resonance from the multiphase microstructure and two-magnon scattering at anisotropy inhomogeneities make an additional contribution to the extrinsic damping of the films. As a result, the film annealed at 450 °C achieves a high full width at half maximum Δf up to 6 GHz for the imaginary part of the frequency-dependent permeability. These films could be novel candidates for the electromagnetic shielding applications.