Effect of a weak external electric field on the kinetics of the ordering of ferroelectrics upon first-order phase transitions

The kinetics of the formation and growth of 180$^\circ$ domains in a weak quasi-stationary external electric field has been considered in the framework of the phenomenological Ginzburg–Landau model using the example of sodium nitrite (NaNO$_2$) crystals that undergo a first-order ferroelectric phase transition of the order–disorder type. The influence of the rate and temperature of quenching, as well as the strength of an external electric field, on the subsequent evolution of the system toward the thermodynamic equilibrium state has been analyzed. It has been shown that, by varying a weak external electric field applied to the ferroelectric crystal after quenching, it is possible to obtain both single-domain and multi-domain ordered structures. It has been established that the formation of nonequilibrium (“virtual”) multi-domain structures of the asymmetric type is possible for particular strengths of the electric field applied to the ferroelectric after quenching. A similar effect can be achieved by varying the depth of quenching of the sample. It has been found that, if the size of the order parameter inhomogeneities formed at the stage of quenching does not exceed a critical value, they can be reoriented partially or completely into domains of opposite sign. For this purpose, the relaxation after quenching should be performed in an external electric field of the appropriate sign.