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 ? = ?´-j ?" 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 ?´ 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 ?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.