Pressure-Driven Spin Crossover Involving Polyhedral Transformation in Layered Perovskite Cobalt Oxyfluoride.

ABSTRACT: We report a novel pressure-driven spin crossover in layered cobalt oxyfluoride Sr₂CoO₃F with a distorted CoO₅ square pyramid loosely bound with a fluoride ion. Upon increasing pressure, the spin state of the Co(III) cation gradually changes from a high spin state (S?=?2) to a low spin state (S?=?0) accompanied by a anomalously large volume contraction (bulk modulus, 76.8(5) GPa). The spin state change occurs on the CoO₅ pyramid in a wide pressure range, but the concomitant gradual shrinkage of the Co-F bond length with pressure gives rise to a polyhedral transformation to the CoO₅F octahedron without a structural phase transition, leading to the full conversion to the LS state at 12?GPa. The present results provide new effective strategy to fine-tune electronic properties of mixed anion systems by controlling the covalency in metal-ligand bonds under pressure.

SUBMITTER: Tsujimoto Y 

PROVIDER: S-EPMC5090247 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature