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arXiv · 0706.2217

Unusual superexchange pathways in a Ni triangular lattice of NiGa$_2$S$_4$ with negative charge-transfer energy

K. Takubo·T. Mizokawa·J. -Y. Son·Y. Nambu·K. Onuma·H. Tonomura·S. Nakatsuji·Y. Maeno
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Abstract

We have studied the electronic structure of the Ni triangular lattice in NiGa$_2$S$_4$ using photoemission spectroscopy and subsequent model calculations. The cluster-model analysis of the Ni 2$p$ core-level spectrum shows that the S 3$p$ to Ni 3$d$ charge-transfer energy is $\sim$ -1 eV and the ground state is dominated by the $d^9L$ configuration ($L$ is a S 3$p$ hole). Cell perturbation analysis for the NiS$_2$ triangular lattice indicates that the strong S 3$p$ hole character of the ground state provides the enhanced superexchange interaction between the third nearest neighbor sites.

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K. Takubo, T. Mizokawa, J. -Y. Son, Y. Nambu, K. Onuma, H. Tonomura, S. Nakatsuji, Y. Maeno. 2007-06-16. Unusual superexchange pathways in a Ni triangular lattice of NiGa$_2$S$_4$ with negative charge-transfer energy. https://doi.org/10.1103/physrevlett.99.037203

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