Electronic structure and metal-insulator transition in SrTi1-xRuxO3

We studied the changes in the electronic structure of SrTi1-xRuxO3 across the metal-insulator transition. The parent compound, SrTiO3, is a well known diamagnetic insulator; whereas the doped compound, SrTi1-xRuxO3, becomes a ferromagnetic metal above x(C) = 0.35. The techniques used in the study were photoemission (PES) and O 1s X-ray absorption (XAS) spectroscopy. The experimental spectra were analyzed in terms of band structure and Hubbard model calculations. The PES and XAS spectra of SrTi1-xRuxO3 show the Ru 4d bands growing in the band gap of SrTiO3. The analysis in terms of the Hubbard model indicates that the Ti 3d and Ru 4d bands are mostly decoupled. This suggests that the metal-insulator transition is a percolation transition like that of metals embedded in a rare gas matrix. Electron correlation effects are present in this system, but they do not seem to play a major role in the transition.