Anomalous low-temperature behavior of the Co dimers in the oxo-halide CoSb{sub 2}O{sub 3}Br{sub 2}

Journal Article · Wed Oct 15 00:00:00 EDT 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.07.005· OSTI ID:21212064

Hugonin, Zuzana ^[1]; Johnsson, Mats ^[1]; Lidin, Sven ^[1]; Wulferding, Dirk ^[2]; Lemmens, Peter ^[2]

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1. Department of Inorganic Chemistry, Stockholm University, S-106 91 Stockholm (Sweden)
2. Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig (Germany)

We report the synthesis, crystal structure determination, magnetic and low-temperature structural properties of a new cobalt antimony oxo-bromide. CoSb{sub 2}O{sub 3}Br{sub 2} crystallizes in the triclinic crystal system, space group P-1, with the following lattice parameters: a=5.306(3) A, b=7.812(4) A, c=8.0626(10) A, {alpha}=88.54(3){sup o}, {beta}=82.17(3){sup o}, {gamma}=80.32(4){sup o}, and Z=2. The crystal structure was solved from single crystal X-ray data and refined on F{sup 2}, R{sub 1}=3.08. The structure consists of layers made up by three building blocks, [CoO{sub 4}Br{sub 2}], [SbO{sub 3}Br], and [SbO{sub 3}] that are connected via edge- and corner-sharing so that structural Co-Co dimers are formed. The layers have no net charge and are only weakly connected by van der Waals forces to adjacent layers. Above {approx}25 K the magnetic susceptibility is independent of the magnetic field and can be very well described by a Curie-Weiss law. Below 25 K the susceptibility passes through a maximum and decreases again that is typical for the onset of long-range antiferromagnetic correlations. Long-range antiferromagnetic ordering is observed below T{sub N}{approx}9 K indicating substantial inter-dimer exchange coupling between Co-Co dimers within the layers. However, according to the heat capacity results only a minute fraction of the entropy is associated with the long-range ordering transition. The phonon anomalies observed for T<6 K in Raman scattering and an anomaly in the specific heat point to a structural instability leading to a loss of inversion symmetry at lowest temperatures. - Graphical abstract: The synthesis, crystal structure determination, and magnetic properties of the new layered compound CoSb{sub 2}O{sub 3}Br{sub 2} is reported. Structural Co-Co dimers are formed within the layers. The susceptibility below 25 K is typical for the onset of long-range antiferromagnetic correlations. Raman scattering and specific heat measurements both point to a structural instability leading to a loss of inversion symmetry below 6 K.

• OSTI ID: 21212064
• Journal Information: Journal of Solid State Chemistry, Vol. 181, Issue 10; Other Information: DOI: 10.1016/j.jssc.2008.07.005; PII: S0022-4596(08)00371-X; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANTIFERROMAGNETISM
ANTIMONY COMPOUNDS
COBALT COMPOUNDS
CRYSTAL STRUCTURE
CURIE-WEISS LAW
DIMERS
ENTROPY
LATTICE PARAMETERS
LAYERS
MAGNETIC SUSCEPTIBILITY
MONOCRYSTALS
OXYBROMIDES
RAMAN EFFECT
SPACE GROUPS
SPECIFIC HEAT
SYMMETRY
SYNTHESIS
VAN DER WAALS FORCES
X RADIATION