Measurement of microwave properties of magnetic particulate composites

The authors have measured the microwave complex permeability in the frequency range 2-18 GHz of a series of particulate composite specimens consisting of iron particles of various sizes in the range 10-150 μm dispersed in a wax matrix at various volume loadings. The results are compared with a theoretical model based on the magnetic polarisability of a spherical conducting particle due to eddy currents induced by the incident magnetic field. They used the model to subtract the eddy current effect to reveal the fundamental ferromagnetic response of the iron and highlight the theoretical and experimental problems that arise