title: Synthesis and Characterization of Ba[CoSO]: Magnetic Complexity in the Presence of Chalcogen Ordering.
abstract: Barium thio-oxocobaltate(II), Ba[CoS2/2 O2/2 ], was synthesized by the reaction of equimolar amounts of BaO, Co, and S in closed silica ampoules. The title compound (Cmcm, a=3.98808(3), b=12.75518(9), c=6.10697(4) Å) is isostructural to Ba[ZnSO]. The use of soft X-ray absorption spectroscopy confirmed that cobalt is in the oxidation state +2 and tetrahedrally coordinated. Its coordination consists of two sulfur and two oxygen atoms in an ordered fashion. High-temperature magnetic susceptibility data indicate strong low-dimensional spin-spin interactions, which are suggested to be closely related to the layer-type crystal structure and perhaps the ordered distribution of sulfur and oxygen. Antiferromagnetic ordering below TN =222 K is observed as an anomaly in the specific heat, coinciding with a significant lowering of the magnetic susceptibility. Density functional theory calculations within a generalized-gradient approximation (GGA)+U approach identify an antiferromagnetic ground state within the square-like two-dimensional layers of Co, and antiferromagnetic correlations for nearest and next nearest neighbors along bonds mediated by oxygen or sulfur. However, this magnetic state is subject to frustration by relatively strong interlayer couplings.
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany). martin.valldor@cpfs.mpg.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Valldor
authors.affiliation: Leibniz Institute for Solid State and Materials Research, Helmholtzstrasse 20, 01069 Dresden (Germany).
authors.forename: Ulrich K
authors.initials: UK
authors.lastname: Rößler
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany).
authors.forename: Yurii
authors.initials: Y
authors.lastname: Prots
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany).
authors.forename: Chang-Yang
authors.initials: CY
authors.lastname: Kuo
authors.affiliation: Institute of Physics, National Chiao Tung University, Hsinchu 30010 (Taiwan).
authors.forename: Jen-Che
authors.initials: JC
authors.lastname: Chiang
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany).
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Hu
authors.affiliation: National Synchrotron Radiation Research Centre, Hsinchu 30076 (Taiwan).
authors.forename: Tun-Wen
authors.initials: TW
authors.lastname: Pi
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany).
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Kniep
authors.affiliation: Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany).
authors.forename: Liu Hao
authors.initials: LH
authors.lastname: Tjeng
keywords: X-ray absorption spectroscopy; anions; chalcogens; cobalt; density functional calculations; magnetic properties