Soft-magnetic properties of Fe–Co–B thin films for ultra-high-frequency applications

Fe 67 Co 18 B 15 amorphous thin films were sputter deposited on glass substrates under a uniform applied magnetic field. The films exhibit excellent soft-magnetic properties of 4πMs∼17.5 kG, Hc∼0.3 Oe, and Hk (anisotropy field) ∼22 Oe. The ultra-high-frequency performance on these films was studied and the relative permeability μ′ is shown to be as high as ∼740 and almost constant to at least 1 GHz. The combination of high 4πMs and relatively high Hk in these films is believed to be partly responsible for the excellent ultra-high-frequency behavior. The soft-magnetic properties of these films show a strong dependence on the film deposition bias voltage, which presumably changes the microstructure of the films and the related magnetic anisotropy.