La2Co2Se2O3: a quasi-two-dimensional mott insulator with unusual cobalt spin state and possible orbital ordering

Authors

Cao Wang, Zhejiang UniversityFollow
Ming-qiu Tan, Zhejiang University
Chun-mu Feng, Zhejiang University
Zhif-eng Ma, Zhejiang University
Shuai Jiang, Zhejiang University
Zhu-an Xu, Zhejiang University
Guang-han Cao, Zhejiang University
Kazuyuki Matsubayashi, University Of Tokyo
Yoshiya Uwatoko, University Of Tokyo

RIS ID

69952

Publication Details

Wang, C., Tan, M., Feng, C., Ma, Z., Jiang, S., Xu, Z., Cao, G., Matsubayashi, K. & Uwatoko, Y. (2010). La₂Co₂Se₂O₃: a quasi-two-dimensional mott insulator with unusual cobalt spin state and possible orbital ordering. Journal of the American Chemical Society, 132 (20), 7069-7073.

Abstract

The new oxyselenide La₂Co₂Se₂O₃, containing Co₂O square-planar layers, has been successfully synthesized using solid-state reactions under vacuum. The compound crystallizes in space group I4/mmm with lattice parameters a = 4.0697(8) Å and c = 18.419(4) Å. Magnetic susceptibility measurements indicate an antiferromagnetic transition at 220 K. The magnetic entropy associated with the transition is close to R ln 2, suggesting an unusual low-spin state for the Co²⁺ ions. The as-prepared sample shows insulating behavior with room-temperature resistivity of 10⁷ Ω cm, which decreases by 4 orders of magnitude under a pressure of 7 GPa. Band structure calculations using the LSDA+U approach reproduce the insulating ground state with low spin for Co and suggest strong orbital polarization for the valence electrons near the Fermi level. It is also revealed that the spin and orbital degrees of freedom in the antiferromagnetic checkerboard spin−lattice are mutually coupled.