Pressure-Driven Spin Crossover Involving Polyhedral Transformation in Layered Perovskite Cobalt Oxyfluoride.
We report a novel pressure-driven spin crossover in layered cobalt oxyfluoride Sr2CoO3F with a distorted CoO5square 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 CoO5pyramid 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.
Research Institute for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Ibaraki 305-0044, Japan.
Yoshihiro
Y
Tsujimoto
Research Institute for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Ibaraki 305-0044, Japan.
Satoshi
S
Nakano
Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
Naoki
N
Ishimatsu
Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
Masaichiro
M
Mizumaki
Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
Naomi
N
Kawamura
Department of Physics, College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan.
Takateru
T
Kawakami
Research Network and Facility Services Division, National Institute for Materials Science, 1-2-1 Sengen, Ibaraki 305-0047, Japan.
Yoshitaka
Y
Matsushita
Research Institute for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Ibaraki 305-0044, Japan.
Kazunari
K
Yamaura