FIELD-INDUCED MAGNETIC TRANSITIONS IN THE ONE-DIMENSIONAL COMPOUND CA3CO2O6

Magnetization measurements on the one-dimensional oxide Ca3Co2O6 havin g a triangular net of Co2O6 chains have been carried out both in stati c and pulsed high magnetic fields. The M/H vs. T curve obeys the Curie -Weiss law at high temperatures. Below 25 K, however, M/H increases ab ruptly, and a plateau is observed at 1/3 of the full moment in the M-H curve, suggesting a ferrimagnetic state of the ferromagnetic chains d ue to the antiferromagnetic interchain interaction. At low H, this sys tem is considered to be in a partially disordered antiferromagnetic st ate for 10 K < T < 25 K and in a ferrimagnetic state below 10 K. The o bserved plateau in the M-H curve for T less than or equal to 5 K is br oader than for 10 K less than or equal to T less than or equal to 20 K ; indicating spin freezing at lower temperatures. The results can be d iscussed in terms of the triangular Ising spin systems.