Universal metastability of the low-spin state in Co${}^{2+}$ systems: non-Mott type pressure-induced spin-state transition in CoCl${}_2$

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.

6 pages, 4 figures

References in corpus (7)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Magnetic Moment Collapse-Driven Mott Transition in MnO
• Spin state transition and covalent bonding in LaCoO3
• Disproportionation and Metallization at Low-Spin to High-Spin Transition in Multiorbital Mott Systems
• Metal-ligand interplay in strongly-correlated oxides: a parametrized phase diagram for pressure induced spin transitions
• Pressure-Driven Orbital Selective Insulator to Metal Transition and Spin State Crossover in Cubic CoO

Cited by in corpus (1)

• Intrinsic ferromagnetism and quantum anomalous Hall effect in CoBr2 monolayer