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Formation of an unconventional Ag valence state in Ag2NiO2

M. D. Johannes·S. Streltsov·I. I. Mazin·D. I. Khomskii
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Abstract

The Ag ion in the recently synthesized novel material Ag2NiO2 adopts an extremely unusual valency of 1/2, leaving the Ni ion as 3+, rather than the expected 2+. Using first principles calculations, we show that this mysterious subvalent state emerges due to a strong bonding-antibonding interaction between the two Ag layers which drives the lower band beneath the O p complex, eliminating the possibility of a conventional Ag 1+ valence state. The strong renormalization of the specific heat coefficient, gamma, is likely due to strong spin fluctuations that stem from nearly complete compensation of the ferro- (metallic double exchange and the 90 degree superexchange) and antiferromagnetic (conventional superexchange via Ni-O-Ag-O-Ni path) interactions.

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M. D. Johannes, S. Streltsov, I. I. Mazin, D. I. Khomskii. 2006-08-08. Formation of an unconventional Ag valence state in Ag2NiO2. https://doi.org/10.1103/physrevb.75.180404

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