Transient Dielectric Behavior during the Commensurate-to-Incommensurate Phase Transition in Rb2ZnCl4

The kinetic process of the commensurate-to-incommensurate phase transition in Rb 2 ZnCl 4 has been studied by tracing the time variations of the polarization and dielectric constant during the transition induced by removing the applied high dc electric field from the sample. The polarization shows an abrupt dropat the instant of field removal and then decays monotonically. The dielectric constant first increases, reaches a maximum and then decreases toward the thermal equilibrium value. The relaxation process slows down as T c is approached from above. A qualitative explanation of the observed transient characteristics is presented on the basis of a nucleation model. It is suggested that at an early stage of the transition the nucleated discommensurations are spaced more widely than in the final thermal equilibrium state.