Frequency dispersion of complex permeability in Mn-Zn and Ni-Zn spinel ferrites and their composite materials

Complex permeability spectra mu*=mu'-imu" for two types of spinel ferrites (Ni-Zn ferrite and Mn-Zn ferrite) and their composite materials have been investigated. The contribution of domain-wall and natural resonance to the permeability spectra was estimated by the numerical fitting of actual measurement data to a simple formula. Frequency dispersion type of each component, relaxation or resonance, can be estimated from one of the fitting parameters, damping factor. In sintered Mn-Zn ferrite, domain-wall contribution is dominant and gyromagnetic spin resonance or relaxation-type magnetization rotation is large in Ni-Zn ferrite. However, relaxation character is dominant in both Mn-Zn and Ni-Zn ferrite composite materials. In composite materials, the permeability value can be scaled by the ferrite particle content using a simple model concerning demagnetizing field. This analysis is useful in designing the permeability spectra of ferrite composite materials. (C) 2003 American Institute,of Physics.