Electronic states of La1-xCaxMnO3 from photoelectron spectroscopy

The electron photoemission spectra from core-levels as well as from the valence bands of the manganese perovskites La0.67Ca0.33MnO3, La0.63Ca0.37Mn0.92Fe0.08O3 and (La0.57Tb0.10)Ca0.33MnO3 have been measured in insulating paramagnetic state at 300 K. The valence band spectra show a two-peak structure at about 3.0 and 5.7 eV below the upper edge of the valence band. Comparing the spectra with the high-resolution spectra measured at 110 eV synchrotron radiation the strong hybridisation of Mn 3d-O 2p states contributing to the valence band has been confirmed. The higher binding energy part of valence band spectrum of Th-doped specimen shows a third feature whose physical origin is discussed. The values of the on-site Coulomb correlation energies in Mn 3d states U-dd, in O 2p states U-pp, the charge transfer energy Delta and the hybridisation energy between Mn 3d and O 2p states T were estimated from the Mn 2p spectra and Auger spectra analysed together with the relevant valence band spectra. Some results are compared with the Mn-55 nuclear magnetic resonance data. (C) 2001 Elsevier Science B.V. All rights reserved.