  We have performed field-swept 59Co NMR measurements on the 'exotic'
spin-chain material, Ca3Co2O6, crystallizing in K4CdCl6-type rhombohedral
structure, believed to exhibit two magnetic transition temperatures (around 24
and 12 K). This is the first NMR investigation of this family of compounds. We
are able to detect the NMR signal below about 15 K, which is a conclusive proof
for the existence of non-magnetic Co ions (Co3+ - low-spin 3d6, in addition to
magnetic Co ions) at least in a narrow temperature range around 10 K, thereby
resolving a controversy on this issue in the literature. In addition, we find
that the spin-lattice and spin-spin relaxation times undergo a dramatic
increase below about 12 K, with a profound influence on the intensity of the
NMR signal as a function of temperature, providing a microscopic evidence for
the existence of 12K-transition. The spectral features present quite an
interesting situation.

Strongly Correlated Electrons;Materials Science