Abstract
The metamagnetic compound CoBr 2.2H 2O has been examined in the temperature range between 1.2 and 40 K. Longrange order of AFM sign sets in at 9.21 ±0.02 K. The complete H-T phase diagram was constructed from the field-dependent susceptibilities. The triple point, where the antiferromagnetic, ferrimagnetic and paramagnetic phases meet, occurs at 7.1±0.1 K and 17.0±0.1 kOe. Two new phase transitions are observed at liquid-helium temperature in addition to the two that are already known. An explanation for the occurence or absence of the anomalies in the X ( H) curves is given on basis of the relaxation-time constants as measured at the phase transitions. The exchange interactions between the cobalt ions in different ferromagnetic chains are calculated, being J 1/ k=-2.77±0.02 K, J 2/ k=-1.20±0.05 K, J 3/ k=-0.02±0.05 K. Several other slight anomalies observed in the X ( H) curves are explained considering irregular spin sites at domain boundaries.
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