Temperature dependent negative permittivity in solid solutions Sr2Mn1-xSnxO4 (x=0, 0.3, 0.5)

A few compositions of the system Sr2Mn1-xSnxO4 (x = 0.0, 0.3, 0.5) were synthesized in the air by the solid-state ceramic route. A change in the sign (positive to negative) of the permittivity above a particular temperature (TC) is observed at all the measured frequencies. The negative permittivity was analyzed by the Drude-Lorentz model. It was found that negative permittivity is caused by the plasma oscillations of thermally excited free charge carriers. Analysis of XPS spectra confirmed the presence of mixed-valence states of both Mn (Mn4+ and Mn3+) and Sn (Sn4+ and Sn2+) ions. The UV-vis.-IR spectroscopy results indicated generation of a large number of defect states in the forbidden bandgap region of Sr2MnO4 on the substitution of Sn at Mn site. Synthesized samples are promising metamaterials for radio frequency (10 Hz-2 MHz) region applications due to the high -temperature plasmonic behavior.

Automated summary

Several compositions of Sr2Mn1-xSnxO4 system were synthesized using solid-state ceramic method in air. A change in the sign of the permittivity above a specific temperature was observed at all frequencies, and it was found that this negative permittivity was caused by plasma oscillations of thermally excited free charge carriers. XPS analysis confirmed mixed-valence states of Mn (Mn4+ and Mn3+) and Sn (Sn4+ and Sn2+) ions, while UV-vis.-IR spectroscopy results indicated the generation of defect states in the forbidden bandgap region of Sr2MnO4 on Sn substitution at Mn site. These synthesized samples show promise as metamaterials for applications in the radio frequency (10 Hz-2 MHz) region due to their high-temperature plasmonic behavior.