Hu, Z and Golden, MS and Fink, J and Kaindl, G and Warda, SA and Reinen, D and Mahadevan, Priya and Sarma, DD (2000) Hole distribution between the Ni 3d and O 2p orbitals in Nd2-xSrxNiO4-delta. In: Physical Review B, 61 (05). pp. 3739-3744.
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We present a joint experimental and theoretical study of x-ray absorption at the O-K and Ni-L-2.3 thresholds of Nd2-xSrxNiO4-delta providing an analysis of the distribution of doped holes induced by Sr substitution between Ni 3d and O 2p orbitals. The preedge peak in the O-K x-ray absorption (XAS) spectra, reflecting holes located in the O 2p orbitals, increases monotonically with the degree of Sr doping up to the maximum doping level studied (x=1.4). The saturation in the relative intensity of the O-K preedge peak in the analogous lanthanum nickelate reported in the literature is shown to be most likely due to surface oxygen deficiency. Furthermore, the experimental Ni-L-2.3 XAS spectrum of the Ni(III) nickelate Nd1.1ST0.9NiO3.95 was simulated by a cluster approach, including charge-transfer and complete multiplet interactions, and compared with the corresponding spectrum of the Ni(III) system Nd2Li0.5Ni0.5O4. The 3d(7) weight in the ground state of Nd1.1Sr0.9NiO3.95 was found to be 42%, somewhat smaller than the value of 51% found for Nd2Li0.5Ni0.5O4. This indicates the influence of nonlocal effects in x-ray-absorption spectroscopy, which, in this case is due to the increased covalency in the Sr-doped system as a result of inter-NiO6-cluster interaction. Such interactions are absent in Nd2Li0.5Ni0.5O4, which is characterized by having isolated NiO6 clusters.
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs to American Physical Society.|
|Department/Centre:||Division of Chemical Sciences > Solid State & Structural Chemistry Unit|
|Date Deposited:||12 Aug 2009 08:34|
|Last Modified:||19 Sep 2010 04:58|
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