LAUSR

Complex permittivity and permeability spectra of Au/Fe₅₃Ni₄₇ hybrid granular composite materials containing spherical Au and Fe₅₃Ni₄₇ microparticles have been investigated from RF to microwave frequency range. In the 80 vol.% composite containing Au/Fe₅₃Ni₄₇ hybrid particles, the metallic property was achieved at the critical volume fraction of Au, $\varphi _{C\_{}{\mathbf {Au}}} = 0.04$ by the electrical percolation of hybrid metallic particles; electrical conductivity at 1 kHz becomes more than 0.1 S/cm. A low-frequency plasmonic state with negative permittivity spectrum was observed above $\varphi _{C\_{}{\mathbf {Au}}}$ . Meanwhile, the complex permeability of the hybrid composites showed a Lorentz-type frequency dispersion with the negative permeability spectrum caused by the magnetic resonance at several hybrid particle contents. Consequently, double negative permittivity and permeability spectra have been realized from about 100 MHz to several gigahertz.