THEORETICAL AND EXPERIMENTAL STUDIES ON THE ELECTRONIC-STRUCTURE OF M(2)O(3) (M=TI, V, CR, MN, FE) COMPOUNDS BY SYSTEMATIC ANALYSIS OF HIGH-ENERGY SPECTROSCOPY

A systematic investigation of 2p core-level X-ray photoemission spectr a (2pXPS) of a series of transition metal (TM) sesquioxides M(2)O(3) ( M = Ti, V, Cr, Mn, Fe) is reported. Theoretical analysis was carried o ut by means of an MO(6) cluster model with the full multiplet structur e of the M ion and the calculated results of the 2pXPS are in good agr eement with the experimental data. Moreover, theoretical and experimen tal investigations of 3pXPS, 3sXPS, valence XPS and bremsstrahlung iso chromat spectra (BIS) of Cr2O3 were also performed and all of these ex perimental data are satisfactorily reproduced with the cluster model a pproach. The character of the insulating energy gap of these M(2)O(3) compounds was also studied based on the spectral analysis. It is shown that the M(2)O(3) compounds from Ti2O3 to Mn2O3 are classified as int ermediate-type insulators between charge transfer (CT) and Mott-Hubbar d (MH) insulators, and Fe2O3 is classified as a CT insulator.