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Johnsson

Mats Johnsson

Universitetslektor

Johnsson

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

Författare

  • Zuzana Hugonin
  • Mats Johnsson
  • Sven Lidin
  • Dirk Wulferding
  • Peter Lemmens
  • Reinhard K. Kremer

Summary, in English

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.

Publiceringsår

2008-01-01

Språk

Engelska

Sidor

2776-2782

Publikation/Tidskrift/Serie

Journal of Solid State Chemistry

Volym

181

Issue

10

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Nyckelord

  • Crystal structure determination
  • Inversion symmetry
  • Lone-pair elements
  • Magnetic susceptibility
  • Oxo-halide
  • Raman scattering

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0022-4596