High Frequency Magnetic Properties of Iron Based Magnetic Particulate Powders

The high frequency magnetic properties (Complex intrinsic permeability pi and effective permeability pe) have been studied for iron based magnetic particulate materials and composite with non-magnetic matrix. The complex relative intrinsic permeability spectra of iron based magnetic particulate powders were calculated with the Soohoo model. Effective permeability of composite consisting of Fe inclusions embedded in a nonmagnetic matrix (epoxy resin) was calculated using Bruggeman's effective medium theory. The theoretically calculated permeability spectra were then compared with experimentally measured permeability spectra of the composite. The measured permeability pmax' and resonant frequency is 2.5-2.8 and around several GHz, respectively, for composites with 30% (by volume) carbonyl iron powders. The parameters indicate that iron based composites possess suitable high frequency magnetic properties for use as electromagnetic materials with low reflectivity at microwave frequencies. The results also showed that the Soohoo model is suitable for simulation of high frequency magnetic properties of ferromagnetic iron based powders.