ELECTRON SPECTROSCOPIC INVESTIGATION OF THE SEMICONDUCTOR-METAL TRANSITION IN LA1-XSRXMNO3

We study the electronic structure of La1-xSrxMnO3+delta, x=0, 0.1, 0.2 , 0.3, and 0.4, across the semiconductor-metal transition, using vario us electron spectroscopy techniques. The negligible intensity seen at E(F) using ultraviolet photoemission spectroscopy and bremsstrahlung i sochromat spectroscopy (BIS) indicate an unusual semiconductor-metal t ransition observed for x greater-than-or-equal-to 0.2, consistent with the resistivity data. The BIS spectra show doped hole states developi ng about 1.4 eV above E(F) as a function of x. Auger electron spectros copy gives an estimate of the intra-atomic Coulomb energy in the O 2p manifold to be about 6.8 eV. The Mn 2p core-level spectrum of LaMnO3, analyzed in terms of a configuration-interaction calculation, gives pa rameter values of the charge-transfer energy DELTA = 5.0 eV, the hybri dization strength between Mn 3d and O 2p states, t=3.8 eV, and the on- site Coulomb energy in Mn 3d states U(dd)=4.0 eV, suggesting a mixed c haracter for the ground state of LaMnO3.