Permeability of Nickel Determined From Microwave Constitutive Parameters of Composites Filled With Nickel Powders

The microwave permeability of nickel is determined from constitutive parameters of paraffin-bound composites filled with nickel flakes or spheres. The metal permeability is calculated with account for skinning. The measurements of constitutive parameters are performed using the reflection-transmission coaxial-line within the frequency band of 0.001-20 GHz. The effects of filling factor, particle shape, and size on permittivity and permeability spectra are analyzed. The retrieval of inclusion permeability is based on the treatment of measured dependence of composite constitutive parameters on frequency and on volume fraction of inclusions. The retrieval procedure is based on the generalized Sihvola mixing model simplified for a single-dimension composite. The model describes the wide contrast of component susceptibility, accounts for inclusion shape and the Bergman-Milton spectral linewidth. The retrieved microwave permeability is close to the values reported for measurements with thick wires and foils.