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Direct Observation of Charge Order in Triangular Metallic AgNiO2 by Single-Crystal Resonant X-Ray Scattering

DOI: 10.1103/PhysRevLett.106.157206 DOI Help
PMID: 21568611 PMID Help

Authors: G. L. Pascut (University of Oxford) , R. Coldea (University of Oxford) , P. G. Radaelli (University of Oxford) , A. Bombardi (Diamond Light Source) , G. Beutier (CEA, INAC) , I. I. Mazin (Naval Research Laboratory, Washington, D.C. 20375) , M. D. Johannes (Naval Research Laboratory) , M. Jansen (Max-Planck Institut fur Festk¨orperforshung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review Letters , VOL 106 (15)

State: Published (Approved)
Published: April 2011

Abstract: We report resonant x-ray scattering measurements on a single crystal of the orbitally degenerate triangular metallic antiferromagnet 2H-AgNiO2 to probe the spontaneous transition to a triple-cell superstructure at temperatures below TS ¼ 365 K. We observe a strong resonant enhancement of the supercell reflections through the Ni K edge. The empirically extracted K-edge shift between the crystallographically distinct Ni sites of 2.5(3) eV is much larger than the value expected from the shift in final states, and implies a core-level shift of _1 eV, thus providing direct evidence for the onset of spontaneous honeycomb charge order in the triangular Ni layers. We also provide band-structure calculations that explain quantitatively the observed edge shifts in terms of changes in the Ni electronic energy levels due to charge order and hybridization with the surrounding oxygens.

Subject Areas: Physics

Instruments: I16-Materials and Magnetism

Other Facilities: ESRF