Soft Magnetic Properties and High-Frequency Characteristics in FeCoSi/Native-Oxide Multilayer Films

Magnetic properties of FeCoSi/native-oxide multilayer films, prepared by DC magnetron sputtering and exposure to oxygen in a sequence, have been investigated. It is found that the appropriate thicknesses of the native-oxide layers and FeCoSi layers are very important in decreasing coercivity H_c of the multilayered films, which may be caused by the exchange coupling between the FeCoSi particles through the oxide. A minimum H_c value of 8.4 Oe was obtained for the [FeCoSi (20 Aring)native-oxide]₅₀ multilayer film with the largest in-plane uniaxial anisotropy field H_k of 130 Oe. The real part mu\´ of complex permeability of this sample is more than 100 and flattens almost to 2.5 GHz, while the imaginary part mu" is less than 50 for f < 2.5 GHz. The ferromagnetic resonance frequency is as high as 3.9 GHz, implying that the film is promising for high-frequency applications.