Importance of tetrahedral coordination for high-valent transition metal oxides: YCrO\(_4\) as a model system

We have investigated the electronic structure of the high oxidation state material YCrO\(_4\) within the framework of the Zaanen-Sawatzky-Allen phase diagram. While Cr\(^{4+}\)-based compounds like SrCrO\(_3\)/CaCrO\(_3\) and CrO\(_2\) can be classified as small-gap or metallic negative-charge-trans...

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Bibliographic Details
Published in:arXiv.org 2014-08
Main Authors: Tsirlin, A A, Rabie, M G, Efimenko, A, Z Hu, Saez-Puche, R, Tjeng, L H
Format: Article
Language:English
Subjects:
Charge transfer
Electronic structure
Oxidation
Phase diagrams
Photoelectrons
Transition metal oxides
Transition metals
Valence
Valence band
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Summary:We have investigated the electronic structure of the high oxidation state material YCrO\(_4\) within the framework of the Zaanen-Sawatzky-Allen phase diagram. While Cr\(^{4+}\)-based compounds like SrCrO\(_3\)/CaCrO\(_3\) and CrO\(_2\) can be classified as small-gap or metallic negative-charge-transfer systems, we find using photoelectron spectroscopy that YCrO\(_4\) is a robust insulator despite the fact that its Cr ions have an even higher formal valence state of 5+. We reveal using band structure calculations that the tetrahedral coordination of the Cr\(^{5+}\) ions in YCrO\(_4\) plays a decisive role, namely to diminish the bonding of the Cr \(3d\) states with the top of the O \(2p\) valence band. This finding not only explains why the charge-transfer energy remains effectively positive and the material stable, but also opens up a new route to create doped carriers with symmetries different from those of other transition-metal ions.
ISSN:2331-8422
DOI:10.48550/arxiv.1408.2396