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arXiv · 1403.3877

Universal metastability of the low-spin state in Co$^{2+}$ systems: non-Mott type pressure-induced spin-state transition in CoCl$_{2}$

Bongjae Kim·Kyoo Kim·B. I. Min
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Abstract

We have investigated the pressure-induced spin-state transition in Co$^{2+}$ systems in terms of a competition between the Hund's exchange energy ($J$) and the crystal-field splitting ($\Delta_{CF}$). First, we show the universal metastability of the low-spin state in octahedrally coordinated Co$^{2+}$ systems. Then we present the strategy to search for a Co$^{2+}$ system, for which the mechanism of spin-state and metal-insulator transitions is governed not by the Mott physics but by $J$ vs. $\Delta_{CF}$ physics. Using CoCl$_{2}$ as a prototypical Co$^{2+}$ system, we have demonstrated the pressure-induced spin-state transition from high-spin to low-spin, which is accompanied with insulator-to-metal and antiferromagnetic to half-metallic ferromagnetic transitions. Combined with metastable character of Co$^{2+}$ and the high compressibility nature of CoCl$_{2}$, the transition pressure as low as 27 GPa can be identified on the basis of $J$ vs. $\Delta_{CF}$ physics.

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Bongjae Kim, Kyoo Kim, B. I. Min. 2014-03-16. Universal metastability of the low-spin state in Co$^{2+}$ systems: non-Mott type pressure-induced spin-state transition in CoCl$_{2}$. https://doi.org/10.1103/physrevb.89.115131

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