  The magnetic behavior of the Ca3Co2O6 spin chain compound is characterized by
a large Ising-like character of its ferromagnetic chains, set on triangular
lattice, that are antiferromagnetically coupled. At low temperature, T < 7K,
the 3D antiferromagnetic state evolves towards a spin frozen state. In this
temperature range, magnetic field driven magnetization of single crystals
(H//chains) exhibits stepped variations. The occurrence of these steps at
regular intervals of the applied magnetic field, Hstep=1.2T, is reminiscent of
the quantum tunneling of the magnetization (QTM) of molecular based magnets.
Magnetization relaxation experiments also strongly support the occurrence of
this quantum phenomenon. This first observation of QTM in a magnetic oxide
belonging to the large family of the A3BBO6 compounds opens new opportunities
to study a quantum effect in a very different class of materials from molecular
magnets.
