Electronic structure and metal-insulator transition in SrTi

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 xC=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 SrTiO 3 . 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