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Issue 30, 2013
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The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

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Abstract

Complex oxides exhibit a wide range of crystal structures, chemical compositions and physical properties. The underlying drivers determining the complicated structure–composition–property phase diagrams are the relative positions and orbital overlaps between the metal cations and the oxygen anions. Here we report a combined experimental and theoretical investigation of the structure and bonding in a series of lanthanum chromium oxides prepared by molecular beam epitaxy. Of particular interest is the charge state and local coordination of the Cr. We have stabilized LaCrO3, LaCrO4 and La2CrO6 films by controlling the three elemental fluxes during deposition, and have carried out X-ray diffraction, X-ray photoemission, and X-ray absorption spectroscopy, as well as first-principles calculations, to determine structure, charge state, chemical bonding, and electronic structure. Significant changes in bonding character and orbital interaction are revealed with decreasing ligand symmetry from octahedral to tetrahedral Cr coordination. Both LaCrO4 and La2CrO6 with tetrahedrally coordinated Cr show strong pre-edge features in the Cr K-edge near-edge structure whereas LaCrO3 with octahedrally coordinated Cr exhibits very weak pre-edge features. The origin of these pre-edge features is discussed based on various selection rules and ligand symmetry. We also demonstrate an increase in cation–anion orbital hybridization and a decrease in long-range ligand coupling induced by this symmetry reduction. These in turn result in dramatic modifications of the macroscopic optical and magnetic properties.

Graphical abstract: The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

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Publication details

The article was received on 11 May 2013, accepted on 14 Jun 2013 and first published on 14 Jun 2013


Article type: Paper
DOI: 10.1039/C3TC30883A
Citation: J. Mater. Chem. C, 2013,1, 4527-4535
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    The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

    L. Qiao, H. Y. Xiao, S. M. Heald, M. E. Bowden, T. Varga, G. J. Exarhos, M. D. Biegalski, I. N. Ivanov, W. J. Weber, T. C. Droubay and S. A. Chambers, J. Mater. Chem. C, 2013, 1, 4527
    DOI: 10.1039/C3TC30883A

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