Abstract
Spin-state ordering—a periodic pattern of ions with different spin-state configurations along a crystal lattice—is a rare phenomenon, and its possible interrelation with other electronic degrees of freedom remains little explored. Here we perform a structural investigation of the mixed-valence Co homometallic ludwigite . A superstructure consistent with a long-range spin-state ordering is observed between K and K. Intermediate states with mesoscopic correlations are detected below down to K with a change of dimensionality at K. The spin-state correlations are connected to the charge sector as revealed by the abrupt changes in the electrical resistance at and . The evolution of the structural parameters below indicate that the spin crossover is ignited by a moderate degree of thermally induced and charge disorder. Charge and spin-state degrees of freedom can be interrelated in mixed-valence spin-crossover materials, leading to sharp transitions involving intermediate spin-state and charge-correlated states at the mesoscale.
1 More- Received 4 September 2023
- Revised 16 February 2024
- Accepted 11 March 2024
DOI:https://doi.org/10.1103/PhysRevB.109.094115
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