Importance of tetrahedral coordination for high-valent transition metal oxides: YCrO${}_4$ as a model system

Abstract

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.

arXiv comment6 pages, 6 figures

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Cited by in corpus (2)

• Universality in the Electronic Structure of 3d Transition Metal Oxides
• Magnetostriction and ferroelectric state in AgCrS${}_2$