SPONTANEOUS KINETICS OF THE DOMAIN STRUCTURE OF TRIGLYCINE SULFATE NEAR THE CURIE POINT

Abstract

The kinetics of non-equilibrium stripe domain structure of ferroelectric tryglycine sulfate crystal has been studied within the temperature interval near the Curie point (0.1 K ≤ ΔTC ≤ 1.0 K) by the atomic force microscopy technique in the contact mode of the piezoelectric response. It is shown that under the experimental conditions: i) average velocities <v> of the development of the domains along the crystallographic [100] direction are greater than along [001] due to the greater magnitude of the electric field acting on the sections of the domain boundaries with a smaller radius of curvature; ii) the ratio of the total perimeter of domain boundaries to the number of  domains, i. e. the average perimeter of the domain, is almost constant upon time and increases with the distance from the Curie point; iii) a marked change in the magnitude of the total surface charge of a crystal is observed only near TC  during the first 30 minutes after passing the phase transition, because in these conditions the crystal is an open system, sensitive to external influences, and it is characterized by non-conservative order parameter; iiii) the total perimeter L of the domain walls increases when approaching TC, and its temperature behavior does not obey power law L ~ {(TC - T) / TC} ^−η, predicted by the thermodynamic theory of ferroelectricity with the exponent η = 0.25.

Keywords: atomic force microscopy, triglycine sulphate, domain structure, Curie point, kinetics, coefficient of unipolarity, velocity of the domain walls, perimeter of domains