Electronic structure of a hole doped oxide with a quasi-1D crystal structure Y2-x(Sr,Ca)xBaNiO5

The effect of hole doping into the divalent nickel oxide Y2BaNiO5, which provides a good example of one-dimensional electronic structure in the presence of strong d-d interactions, has been examined by means of several techniques including X-ray absorption and electron energy loss spectroscopies at oxygen K-edges (O K-edges). The crystal structure of this compound shows one-dimensional chains of vertex-sharing NiO6 octahedra running along the z-axis. Hole doping into this material is realized by substituting Ca2+ or Sr2+ ions for the Y3+ ions. We suggest that the doped holes have antibonding Ni 3d(3z(2)-r(2))-O2p(z) character. (C) 2001 Elsevier Science B.V. All rights reserved.