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

Abstract

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.

Frequency-Dependent Effective Material Parameters of Composites as a Function of Inclusion Shape

“…A classical example is related to carbonyl iron composites. Despite almost perfect spherical shape of carbonyl iron particles, the form factor restored from the volume fraction dependence of the permittivity or permeability frequently differs greatly from 1/3 [18,23]. The reason is an agglomeration of the inclusions.…”

Complex permeability and microwave absorption properties of planar anisotropy Ce2Fe17N3−δ particles

“…where n 0 is the shape factor (effective demagnetization factor) of inclusions, and it is customarily used as a fitting parameter to provide an agreement with measured data [16,20]. However, the conclusion was not supported by many experiments [21][22][23].…”

Engineering, Modeling and Testing of Composite Absorbing Materials for EMC Applications

“…The experimental data do not agree with the BSR prediction of %. Moreover, even for a composite containing carbonyl iron powder (CIP) with almost perfect spherical inclusions, the experimentally obtained effective form factor both for permittivity and permeability may significantly deviate from 1/3 (Osipov et al, 2002). This means that the BSR may not be applicable for predicting properties of magnetic composites.…”