Electromagnetic Characteristics of Ni-Zn Ferrite-SiO2 Composites

The relative complex permeability of ferrite composites made of Ni-Zn ferrite and SiO2 is investigated using various raw SiO2 powders with different grain sizes (average grain sizes: 29 microns, 30 nm, 12 nm, 7 nm). If the volume ratio of Ni-Zn ferrite is greater than that of SiO2, the complex permeabilities of both ferrite composites obey Lichtenecker's logarithm mixed law. However, if the volume ratio of Ni-Zn ferrite is less than that of SiO2 and the grain size of SiO2 is sufficiently smaller than that of Ni-Zn ferrite, the frequency dependence of complex permeability agrees with values calculated by assuming a model in which the grains of the magnetic materials are individually located in the dielectric medium. The relative complex permeability of ferrite composites depends on the grain characteristics, and that of ferrite composites whose grains are in contact with each other also obeys Lichtenecker's logarithm mixed law. (Author)