Kinetic Process of the Incommensurate-to-Commensurate Phase Transition in Rb₂ZnCl₄

Abstract

The kinetic process of the incommensurate-to-commensurate phase transition in Rb₂ZnCl₄ has been investigated by the measurements of the time evolution of polarization and dielectric constant during the field-induced transition. The following picture of the phase transition has been obtained. Under a sufficiently strong dc field, the discommensurations (DC’s) are annihilated successively and the number of DC’s decreases. The lattice spacing increases and at the same time the DC lattice becomes considerably disordered. When the lattice spacing has increased to a certain threshold value, regions of the commensurate phase start to appear, they grow and finally cover the whole crystal. The above picture agrees with the result of theoretical study based on the free energy of a system undergoing a first-order commensurate-incommensurate transition.