GLASSY DYNAMICS OF RB0.40(ND4)0.60D2PO4

The complex dielectric constant of Rb0.40(ND4)0.60D2PO4 has been measu red in the frequency interval from 1 mHz to 1 GHz at temperatures betw een 40 and 140 K. A novel frequency-temperature plot of the data is in troduced to show that the behavior of the relaxation spectrum is refle cted in the real part of the dielectric constant. It is found that the highest relaxation frequency f2 = 1/2pitau(min) follows an Arrhenius behavior, whereas the lowest frequency f1 = 1/2pitau(max) exhibits a c ritical decay according to the Vogel-Fulcher law f1 is-proportional-to exp[-U/(T - T0)] with T0 = 32.9 K.