Abstract
Negative permittivity has been researched extensively in a wide range of metamaterials and composites. Using a solid-state ceramic route, a composite of Sr7Mn4O15 - SrO has been produced. Above a specified temperature (Tc), a change in permittivity sign from positive to negative is observed at all measured frequencies (10 Hz-2MHz). Experimental data of real part of permittivity was fitted to Drude-Lorentz oscillator model. Plasma oscillations of thermally excited free carriers have been identified as the cause of negative permittivity. High temperature plasma plasmonic activity of synthesized composite make it promising metamaterial for electromagnetic devices working in the radio frequency (10 Hz -2MHz) range.
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