EFFECT OF L,α-ALANINE IMPURITY ON THE SPONTANEOUS EVOLUTION OF THE DOMAIN STRUCTURE OF TRIGLICINE SULPHATE NEAR THE CURIE POINT

Abstract

Using the atomic force microscopy method in the piezoelectric response mode, the evolution of the nonequilibrium domain structure of pure triglycine sulfate (TGS) crystals and doped with an L, α-alanine (ATGS) impurity was studied near the phase transition temperature over the interval ΔТ_С = Т_С – Т = 1 К. In both crystals the total number of domains N, the total perimeter of domain boundaries L and also the dielectric constant ε, measured in a weak ac electric field, decrease exponentially upon time. The ruggedness of the domain boundaries in the ATGS crystal persists over time, leading to an increase of the average domain perimeter L / N. The average velocity of spontaneous lateral movement of domain boundaries in a TGS crystal is less than in ATGS, due to the damping influence of defects. Near T_C, both crystals are open systems with a non-conservative order parameter, and the development of the domain structure occurs with a change of the surface charge. With distance from the T_C, the state with a conserved order parameter is reached faster in ATGS crystal.