Effect of γ irradiation on the heat capacity of Rb2ZnBr4 in the vicinity of phase transitions

Heat capacity of Rb2ZnBr4 as a function of gamma irradiation dose has been measured within the 85-300 K range by the adiabatic calorimeter technique. It is shown that, as the irradiation dose increases, the heat capacity peak in the vicinity of the incommensurate-commensurate first-order phase transition (PT) decreases, and the transition temperature T-c increases. The heal capacity peak in the region of the second-order PT at T-3 = 112 K does not depend on gamma irradiation, both in magnitude and in position, just as the heat capacity throughout the remainder of the temperature range studied. (C) 1998 American Institute of Physics.