Abstract:
New data on the specific heat, thermal expansion, and magnetization of the CaMn7O12 phase require a revision of the current concepts of the sequence of phase transitions in this compound. It is found that a spin-glass phase transition occurs in CaMn7O12 at TM = 49 K, whereas the transition at TS = 89 K exhibits the features of a first-order phase transition and thereby is apparently of structural origin. In the range TM < T< TS, the CaMn7O12 compound exhibits negative thermal expansion, which is also indicative of structural changes.