Tunable Negative Permittivity with Fano-like Resonance and Magnetic Property in Percolative Silver/Yittrium Iron Garnet Nanocomposites

Composites with negative electromagnetic parameters can be promising candidates for metamaterials. In this paper, the impedance, permittivity, and permeability were investigated in the silver/yrrium iron garnet (Ag/YIG) composites, which was fabricated by in situ synthesis process. In the vicinity of the percolation threshold, the dielectric loss is dominated by conduction and polarization. When the percolative state was reached, the negative permittivity with Fano-like renonance (an asymmetric resonance) was observed. Furthermore, the negative permittivity behavior was attributed to inductive character, and the LC resonance was responsible for the Fano-like transition from negative to positve permittivity. In addition, it was demonstrated that the permeability of Ag/YIG composites presented frequency dispersion due to the domain wall motion and the gyromagnetic spin rotation. The percolative Ag/YIG composites with tunable negative permittivity have great potential in the field of electromagnetic attenuation, shielding, and antenna.