Ferroelectric-ferroelastic domain kinetic studies by deflection of light in an NH₄HSeO₄ crystal

Deflection of light studies of the ferroelectric-ferroelastic domain kinetics under the influence of an external electric field, applied to an NH₄HSeO₄ crystal sample, are presented. Splitting of the deflected A beam was observed in angular measurement for various states of sample polarization. It is also shown that the intensity of deflected beam A depends strongly on the electric field applied to the sample. Detailed studies of the deflected spot intensity were performed. Our calculations allowed us to establish a correlation between domain wall density, controlled by the electric field, and deflection intensity