Role of Ti-Ru interaction in SrTi0.5Ru0.5O3 : Physical properties, x-ray spectroscopy, and cluster model calculations

Abstract

We have performed a systematic study of the physical properties and electronic structure of ${\mathrm{SrTiO}}_{3}, {\mathrm{SrTi}}_{0.5}{\mathrm{Ru}}_{0.5}{\mathrm{O}}_{3}$, and ${\mathrm{SrRuO}}_{3}$. For the mixed compound, the temperature dependence of the magnetization is consistent with the occurrence of $\mathrm{Ru}Ti$ and $\mathrm{Ti}Ru$ defects. Despite being a semiconductor, the behavior of the electrical resistivity as a function of temperature is compatible with the emergence of small metallic regions richer in Ru concentration, a feature supported by the finite spectral weight at the Fermi level observed in the valence-band x-ray photoemission spectroscopy spectrum. The x-ray photoemission and absorption spectra of the ${\mathrm{SrTi}}_{0.5}{\mathrm{Ru}}_{0.5}{\mathrm{O}}_{3}$ compound were simulated by double cluster model calculations, which include the ${\mathrm{TiO}}_{6}\ensuremath{-}{\mathrm{RuO}}_{6}$ interaction, and also by the linear combination of single cluster calculations for ${\mathrm{SrTiO}}_{3}$ and ${\mathrm{SrRuO}}_{3}$. The results indicate that the interaction between different octahedra may give rise to distinct peak characters, depending on the experimental spectrum being calculated. We argue that these effects are only captured with the explicit inclusion of the Ti-Ru interaction.