High frequency permeability of Fe-Al-Si granular composite materials

High-frequency electromagnetic properties of Fe-Al-Si alloy (Sendust) granular composite materials have been studied by measuring their relative complex permeability (μ_r = μ_r\´ - j μ_r") and permittivity (ε_r = ε_r\´ - j ε_r") spectra. The bulk Fe-Al-Si alloy shows metallic electrical conduction, and permeability decreases rapidly with frequency. On the other hand, Sendust powder shows relatively high electrical resistivity. Sendust composite material demonstrates insulating electrical properties up to at least 80 vol.% particle content. Thus the relatively high permeability in the microwave frequency range can be obtained. Frequency dispersion characteristics of permeability for the composite were analyzed by the superposition of domain wall and gyromagnetic spin resonance formula. The particle content variation of permeability can be qualitatively described by a coherent model mixing rule.