FREQUENCY DISPERSION OF PERMEABILITY IN FERRITE COMPOSITE-MATERIALS

Permeability spectra of Ni-Zn ferrite composite materials, prepared by mixing the ferrite particles with EVA resin, have been studied. In the sintered ferrite (volume fraction 1.0), the spin resonance is around 9 MHz and the static permeability about 1400. As the ferrite content decreases (composite materials), the static susceptibility of the spin component decreases and the spin resonance frequency shifts higher. The real part of the permeability in the ferrite composite materials becomes larger than that of the sintered ferrite in the rf frequency region. These features have been analyzed using the magnetic circuit model. The application of Snoek's limit extended to ferrite composite materials is also proposed.