Electronic states of La1-xCaxMnO3 from photoelectron spectroscopy

The electron photoemission spectra from core-levels as well as from the val ence bands of the manganese perovskites La0.67Ca0.33MnO3, La0.63Ca0.37Mn0.9 2Fe0.08O3 and (La0.57Tb0.10)Ca0.33MnO3 have been measured in insulating par amagnetic state at 300 K. The valence band spectra show a two-peak structur e at about 3.0 and 5.7 eV below the upper edge of the valence band. Compari ng the spectra with the high-resolution spectra measured at 110 eV synchrot ron radiation the strong hybridisation of Mn 3d-O 2p states contributing to the valence band has been confirmed. The higher binding energy part of val ence band spectrum of Th-doped specimen shows a third feature whose physica l origin is discussed. The values of the on-site Coulomb correlation energi es in Mn 3d states U-dd, in O 2p states U-pp, the charge transfer energy De lta and the hybridisation energy between Mn 3d and O 2p states T were estim ated from the Mn 2p spectra and Auger spectra analysed together with the re levant valence band spectra. Some results are compared with the Mn-55 nucle ar magnetic resonance data. (C) 2001 Elsevier Science B.V. All rights reser ved.