Photoemission and Hartree-Fock studies of oxygen-hole ordering in charge-disproportionated La1-xSrxFeO3

We have studied the "charge disproportionation" phenomenon in La1-xSrxFeO3 by photoemission spectroscopy and unrestricted Hartree-Fock band-structure calculations. We find a systematic decrease of the spectral intensity near Fermi level (E-F) toward x = 0.67, where the charge disproportion is most s tabilized. The spectra for x = 0.67 show the dearest temperature-dependent changes in the vicinity of E-F across the transition corresponding to the c harge ordering of ''Fe3+'':''Fe5+'' = 2:1. The Hartree-Fock calculations in dicate that ordering of oxygen holes indeed occurs in the charge disproport ionated state. [S0163-1829(99)07831-5].