  Ca3Co2O6 is a system exhibiting a series of fascinating properties, including
magnetization plateaus and remarkably slow dynamics at low-T. These properties
are intimately related to the geometrical frustration, which results from a
particular combination of features: (i) the chains are arranged on a triangular
lattice; (ii) there is a large uniaxial anisotropy; (iii) the intrachain and
interchain couplings are ferromagnetic and antiferromagnetic, respectively.
  The uniaxial anisotropy is thus an issue of crucial importance for the
analysis of the physical properties of Ca3Co2O6. However, it turns out that no
precise investigation of this magnetic anisotropy has been performed so far. On
the basis of susceptibility data directly recorded on single crystals, the
present study reports on quantitative information about the anisotropy of
Ca3Co2O6.
