Dielectric response of SrTiO$_{3}$–SrMg$_{1/3}$Nb$_{2/3}$O$_{3}$ solid solutions in the terahertz–infrared range

The reflection and transmission spectra of ceramic samples of SrTiO$_{3}$–SrMg$_{1/3}$Nb$_{2/3}$O$_{3}$ solid solutions have been measured in the frequency range of 5–5000 cm–1 and in the temperature range of 5–370 K. Based on these spectra, the spectra of the real $\varepsilon'(\nu)$ and imaginary $\varepsilon''(\nu)$ parts of the complex permittivity $\varepsilon^{*}(\nu)$ have been simulated by the method of dispersion analysis. It has been found that the temperature evolution of the dielectric constant is entirely determined by the behavior of the soft mode.