Electromagnetic properties of metal granular composite materials for EMC applications

摘要

Electromagnetic properties of copper and Fe55Ni45 alloy (Permalloy) composite materials have been studied by measuring the relative complex permeability (∊r = ∊r'− j∊r”), and permittivity (εr = εr'− jεr”) spectra over the microwave range, as well as the a.c. electrical conductivity σac spectra. The variation of σac and ∊r with particle content shows the insulator-metal transition due to the percolation effect. The effective cluster model can be applied to the percolation effect in permittivity. The permeability spectra in Permalloy composites, which contain the percolated particles, can be affected by the eddy current effect. The permeability relaxation frequency of Permalloy composites shifts to the higher frequencies by the oxidation of embedded particle surfaces.