GAMMA-RADIATION AND ISOTOPIC EFFECT ON THE CRITICAL-BEHAVIOR IN TRIGLYCINE SELENATE CRYSTALS

Isotopic effects in pure and y-irradiated triglycine selenate crystals were investigated using the specific heat (C(p)) technique. The obtai ned results showed an interesting dependence of the critical behavior of C(p) on the deuterium content. With increasing content of deuterium , the character of the phase transition changed from a second order (l ambda-type) to a first order transition. After gamma-irradiation, the behavior of C(p) around the phase transition region was essentially af fected. The transition temperature, T(c), decreased and DELTAC(p) depr essed, and the transition became broad. It was noted that the effect o f gamma-irradiation is opposite to the isotopic effect.