X-ray spectroscopic techniques are powerful tools for electronic structure investigations of transition metal oxides

Transition metal oxides display uniquely rich physics. Phenomena like superconductivity or colossal magneto resistance are related to collective phase transitions as consequence of a fascinating interplay between the charge, orbital and spin degree of freedom with the crystal lattice. Understanding the underlying electronic properties of transition metal oxides is one major topic in nowadays condensed matter physics. In this paper the investigation of a number of transition metal oxides, with emphasis to ferroelectric and magnetic compounds, by means of different X-ray spectroscopic techniques is presented. X-ray spectroscopic techniques offer unique capabilities for the analysis of spatial distribution of the electron density and chemical bonding. A lot of results shown in this paper are compared to different theoretical electronic structure calculations, i.e. ab initio band structure calculations as well as full multiplet calculations.