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Charge disproportionation and search for orbital ordering in NdNiO3 by use of resonant x-ray diffraction

DOI: 10.1103/PhysRevB.72.155111 DOI Help

Authors: V. Scagnoli (Paul Scherrer Institut) , U. Staub (Paul Scherrer Inst) , M. Janousch (Swiss Light Source) , A. M. Mulders (Swiss Light Source) , M. Shi , G. I. Meijer , S. Rosenkranz , S. B. Wilkins (European Commission, Joint Research Center, Institute for Transuranium Elements) , L. Paolasini (ESRF) , J. Karpinski (Laboratorium für Festkörperphysik) , S. M. Kazakov (Laboratorium für Festkörperphysik) , S. W. Lovesey (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 72 (15)

State: Published (Approved)
Published: October 2005

Abstract: Detailed resonant x-ray diffraction experiments including azimuthal angle scans were performed on NdNiO3 around the Ni K absorption edge, allowing us to investigate the electronic changes associated with the metal-to-insulator transition. The influence on the observed reflections of charge disproportionation and the asphericity of the Ni electron density is evaluated. The asphericity, due to the distortion of the oxygen octahedra, persists also in the metallic phase, but its influence on the unrotated sigma-sigma (033) diffraction signal is found to be negligible, in contrast to the case for the superlattice reflections found in manganites and magnetite. We conclude that the sigma-sigma scattering intensity is consistent with charge disproportionation at the Ni site. No (1/2 0 1/2) type reflections were found, making unlikely the simultaneous occurrence of orbital order with this previously proposed wave vector. Moreover, the asphericity observed in the 4p shell in the metallic state indicates that there is no orbital degeneracy. Therefore, no orbital ordering is expected to occur at the metal-insulator transition.

Subject Areas: Physics

Technical Areas: Theoretical Physics

Added On: 26/04/2010 14:19

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