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Anomalous low-temperature behavior of the Co dimers in the oxo-halide CoSb2O3Br2

Hugonin, Zuzana ; Johnsson, Mats LU ; Lidin, Sven LU ; Wulferding, Dirk ; Lemmens, Peter and Kremer, Reinhard K. (2008) In Journal of Solid State Chemistry 181(10). p.2776-2782
Abstract

We report the synthesis, crystal structure determination, magnetic and low-temperature structural properties of a new cobalt antimony oxo-bromide. CoSb2O3Br2 crystallizes in the triclinic crystal system, space group P-1, with the following lattice parameters: a = 5.306(3) Å, b = 7.812(4) Å, c = 8.0626(10) Å, α = 88.54(3)°, β= 82.17(3)°, γ = 80.32(4)°, and Z = 2. The crystal structure was solved from single crystal X-ray data and refined on F2, R1 = 3.08. The structure consists of layers made up by three building blocks, [CoO4Br2], [SbO3Br], and [SbO3] that are connected via edge- and corner-sharing so that structural Co-Co dimers are... (More)

We report the synthesis, crystal structure determination, magnetic and low-temperature structural properties of a new cobalt antimony oxo-bromide. CoSb2O3Br2 crystallizes in the triclinic crystal system, space group P-1, with the following lattice parameters: a = 5.306(3) Å, b = 7.812(4) Å, c = 8.0626(10) Å, α = 88.54(3)°, β= 82.17(3)°, γ = 80.32(4)°, and Z = 2. The crystal structure was solved from single crystal X-ray data and refined on F2, R1 = 3.08. The structure consists of layers made up by three building blocks, [CoO4Br2], [SbO3Br], and [SbO3] 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 ∼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 TN-9K 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 < 6K 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.

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author
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publishing date
type
Contribution to journal
publication status
published
keywords
Crystal structure determination, Inversion symmetry, Lone-pair elements, Magnetic susceptibility, Oxo-halide, Raman scattering
in
Journal of Solid State Chemistry
volume
181
issue
10
pages
7 pages
publisher
Academic Press
external identifiers
  • scopus:55349107770
ISSN
0022-4596
DOI
10.1016/j.jssc.2008.07.005
language
English
LU publication?
no
id
70895007-6b2e-4833-9522-03da9d48f028
date added to LUP
2019-04-08 15:10:36
date last changed
2025-01-09 05:50:16
@article{70895007-6b2e-4833-9522-03da9d48f028,
  abstract     = {{<p>We report the synthesis, crystal structure determination, magnetic and low-temperature structural properties of a new cobalt antimony oxo-bromide. CoSb<sub>2</sub>O<sub>3</sub>Br<sub>2</sub> crystallizes in the triclinic crystal system, space group P-1, with the following lattice parameters: a = 5.306(3) Å, b = 7.812(4) Å, c = 8.0626(10) Å, α = 88.54(3)°, β= 82.17(3)°, γ = 80.32(4)°, and Z = 2. The crystal structure was solved from single crystal X-ray data and refined on F<sup>2</sup>, R<sub>1</sub> = 3.08. The structure consists of layers made up by three building blocks, [CoO<sub>4</sub>Br<sub>2</sub>], [SbO<sub>3</sub>Br], and [SbO<sub>3</sub>] 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 ∼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</sub>-9K 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 &lt; 6K 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.</p>}},
  author       = {{Hugonin, Zuzana and Johnsson, Mats and Lidin, Sven and Wulferding, Dirk and Lemmens, Peter and Kremer, Reinhard K.}},
  issn         = {{0022-4596}},
  keywords     = {{Crystal structure determination; Inversion symmetry; Lone-pair elements; Magnetic susceptibility; Oxo-halide; Raman scattering}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{10}},
  pages        = {{2776--2782}},
  publisher    = {{Academic Press}},
  series       = {{Journal of Solid State Chemistry}},
  title        = {{Anomalous low-temperature behavior of the Co dimers in the oxo-halide CoSb<sub>2</sub>O<sub>3</sub>Br<sub>2</sub>}},
  url          = {{http://dx.doi.org/10.1016/j.jssc.2008.07.005}},
  doi          = {{10.1016/j.jssc.2008.07.005}},
  volume       = {{181}},
  year         = {{2008}},
}