Radio-frequency permeability and permittivity spectra of copper/yttrium iron garnet cermet prepared at low temperatures

Copper/yttrium iron garnet (Cu/Y3Fe5O12) cermets with tailored microstructures were prepared via a facile wet chemical process. The radio-frequency permeability and permittivity spectra of the cermets were investigated in detail. A percolation phenomenon appears with increasing copper contents, and an ultra-low percolation threshold (<5.47 vol%) is obtained. For the cermets below percolation threshold, the frequency dispersion of permittivity is featured with a poly-dispersive Debye type relaxation process. For the cermets above but still near percolation threshold, plasma-like negative permittivity featured with fano-like resonances was obtained. The Cu/Y3Fe5O12 cermet is a potential candidate for electromagnetic cloaking, microwave attenuation and telecommunications, etc.