  We report the results of 151Eu Moessbauer effect and magnetization
measurements in the Eu-doped Ca3Co2O6 and Ca3CoRhO6, which are of great current
interest in the fields of spin-chain magnetism and geometrical frustration. We
find that there is a pronounced increase in the line-width of the Moessbauer
spectra below a certain characteristic temperature which is well-above the one
at which three-diensional ordering features set in. This unusual broadening of
the spectra indicates the existence of a characteristic temperature in these
'exotic' magnetic systems, attributable to the onset of incipient
one-dimensional magnetic order. This is inferred from an intriguing correlation
of this characteristic temperature with the paramagnetic Curie temperature (a
measure of intrachain coupling strength in these cases).
