Particle Size and Concentration Effect on Permeability and EM-Wave Absorption Properties of Hybrid Ferrite Polymer Composites

Hybrid MnZn/NiZn/PVC polymer composite materials have been prepared using a dry low-temperature hot-pressing process and the influence of particle size, concentration, and the fraction ratio of the dual MnZn/NiZn ferrite filler on their complex permeability mu = mu' - j mu '' and electromagnetic wave (EM-wave) absorbing properties were investigated within the frequency range of 1-3000 MHz. The observed frequency dispersion of permeability was of a relaxation type and caused by a resonance of vibrating domain walls and a natural ferromagnetic resonance of precessing magnetic moments in domains. The complex permeability and resonance frequency f(res) of hybrid composites have been affected mainly by changes in concentration and fraction ratio of ferrite filler: the mu' at low frequency decreased and f(res) shifted towards the higher frequency region with the decrease of ferrite concentration and with the configuration change from the MnZn/PVC composite to NiZn/PVC one. Measured values of complex permeability were used to determine the return loss RL using a model of a single-layered EM-wave absorber backed by a perfect conductor. In the designed single layer absorbers, the RL as well as the matching frequency f(m), matching thickness d(m), bandwidth Delta f for RL <= -20 dB, and the minimum of return loss (RL)(min) seem to be strongly dependent on particle size, concentration, and the fraction ratio of the dual MnZn/NiZn ferrite filler.