Reconstruction of intrinsic parameters of a composite from the measured frequency dependence of permeability

The mixing rules for the permittivity and permeability of composites are known to depend greatly on the microscopic structure of the composite. This dependence can be quantified in terms of Bergman's spectral function. In this paper, the spectral function of actual magnetic composites is reconstructed from their measured microwave constitutive parameters. The samples under study are composed of carbonyl iron or Fe-Cr-Al alloy powders embedded in a paraffin wax matrix. The permittivity and permeability of the samples is measured in the 0.1-10 GHz frequency band. The proposed approach to process the measured data allows the spectral function of the composite and frequency dependence of intrinsic, permeability of inclusions to be derived. The obtained results are in agreement with available tabulated data.