XAS AND XPS STUDY OF ELECTRONIC-STRUCTURE OF THE TRIVALENT CUPRATE LA2LI0.5CU0.5O4-DELTA

Well-characterized stoichiometric La2Li0.5Cu0.5O4-delta (delta almost- equal-to 0.04) has been studied using high resolution CuL3- and OK-edg es absorption (XAS) and Cu 2p3/2 X-ray photoelectron spectroscopy (XPS ) techniques. The system is found not to have any Cu 3d8 configuration in its ground state but instead reveals a high density of the holes c reated by doping of monovalent lithium for the divalent copper in the oxygen 2p levels resulting in a 3d9L copper configuration by charge tr ansfer. The formal valence of copper in it is found to be as high as a lmost-equal-to 2.84 in agreement with chemical analysis. The empirical correlation between the shift of the main XPS line (3d10L) and intens ity ratio of the satellite (3d9) to the main line is examined and, als o, a new correlation between the energy spread of the XPS satellite an d the energy separation of the CuL3 absorption lines due to transition s from (3d9) and (3d9L) states is suggested.