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Spin-orbit induced mixed-spin ground state in $R$NiO$_3$ perovskites probed by XAS: new insight into the metal to insulator transition

C. Piamonteze·F. M. F. de Groot·H. C. N. Tolentino·A. Y. Ramos·N. E. Massa·J. A. Alonso·M. J. Martínez-Lope
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Abstract

We report on a Ni L$_{2,3}$ edges x-ray absorption spectroscopy (XAS) study in $R$NiO$_3$ perovskites. These compounds exhibit a metal to insulator ($MI$) transition as temperature decreases. The L$_{3}$ edge presents a clear splitting in the insulating state, associated to a less hybridized ground state. Using charge transfer multiplet calculations, we establish the importance of the crystal field and 3d spin-orbit coupling to create a mixed-spin ground state. We explain the $MI$ transition in $R$NiO$_3$ perovskites in terms of modifications in the Ni$^{3+}$ crystal field splitting that induces a spin transition from an essentially low-spin (LS) to a mixed-spin state.

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C. Piamonteze, F. M. F. de Groot, H. C. N. Tolentino, A. Y. Ramos, N. E. Massa, J. A. Alonso, M. J. Martínez-Lope. 2004-12-10. Spin-orbit induced mixed-spin ground state in $R$NiO$_3$ perovskites probed by XAS: new insight into the metal to insulator transition. https://doi.org/10.1103/physrevb.71.020406

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