Sm. Butorin et al., ELECTRONIC-STRUCTURE OF LA2-XSRXNIO4-X-RAY ABSORPTION AND EMISSION SPECTROSCOPIES(DELTA STUDIED BY SOFT), Physica. C, Superconductivity, 235, 1994, pp. 1047-1048
The O-K x-ray absorption and emission measurements were performed on L
a2-xSrxNiO4+delta with different delta and x. For doped compounds, a p
repeak is observed near the O 1s edge associated with doping-induced u
noccupied O 2p states. The O-K x-ray emission spectra of La2-xSrxNiO4delta exhibit changes in their profile with variation of the excitatio
n energy through the O 1s edge which are due to the difference in the
absorption cross section for inequivalent O sites and in the degree of
the localization of unoccupied states. Analysis of the results obtain
ed suggests that for the delta>0 sample the states in the O 1s prepeak
are rather localized by trapping the induced holes in small anti-Jahn
-Teller polaron while for the highly Sr-doped compounds these states h
ave itinerant character and belong to mainly in-NiO2-plane oxygen.