ELECTRONIC-STRUCTURE OF LA1-XSRXFEO3

We have investigated the electronic structure of well-characterized sa mples of La1-xSrxFeO3 (x =0.0-0.4) by x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy, bremsstrahlung isochro mat (BI) spectroscopy, and Auger electron spectroscopy. We find system atic behavior in the occupied and unoccupied density of states reflect ing changes in the electronic structure on hole doping via Sr substitu tion as well as providing estimates for different interaction strength s. The spectral features, particularly of the unoccupied states obtain ed from BI spectra, indicate the probable reason for the absence of an insulator-metal transition in this series. Analysis of the Auger spec tra provides the estimates of the on-site effective Coulomb interactio n strengths in Fe 3d and O 2p states. The parameter values for the bar e charge-transfer energy Delta and the Fe 3d-O 2p hybridization streng th t sigma for LaFeO3 are obtained from an analysis of the Fe 2p core- level XPS in terms of a model many-body calculation. We discuss the ch aracter of the ground state in LaFeO3 as well as the nature of the dop ed hole states in La1-xSrxFeO3, based on these parameter values.