Effect of gamma-irradiation on the heat capacity of an [NH2(CH3)(2)](2) center dot CuCl4 crystal in the temperature range 80-300 K

The heat capacity of [NH2(CH3)(2)](2) . CuCl4 crystals prior to and after g amma -irradiation with doses of 1, 5, 10, and 50 MR is measured by the calo rimetric method in the temperature range 80-300 K. It is found that, as the temperature decreases, the temperature dependence C-p(T) exhibits two anom alies which correspond to phase transitions from the incommensurate to the ferroelectric phase at T-c = 281 K and from the ferroelectric to the ferroe lastic phase at T-l = 255 K. The nature of the anomalies is typical of a fi rst-order phase transition. In addition, a smeared anomaly in the form of a small increase in the heat capacity of the ferroelectric phase is observed at T approximate to 275 K. It is demonstrated that when the dose of gamma -irradiation increases, the anomalies decrease in magnitude and the phase t ransition temperatures are displaced: T-c increases and T-l decreases. (C) 2001 MAIK "Nauka/Interperiodica".