IMF2017

The domain structure evolution during polarization reversal in uniform electric field has been studied in potassium titanyl phosphate (KTiOPO4, KTP) single crystals using various complementary experimental methods. The studied KTP samples representing 2-mm-thick plates cut perpendicular to polar axis were grown by top-seeded solution method. The optical microscopy without selective chemical etching has been used for in situ visualization of domain structure evolution with high temporal resolution. The obtained contrast was attributed to local change of the refractive index in the vicinity of the domain wall caused by residual depolarization field. The in situ visualization allowed revealing two elongated domain shapes: stripe and rhombus, oriented along Y direction. Two types of the moving domain walls were distinguished: (a) the walls of the rhombus domains deviated from Y-direction for the angle below 10 degrees (Y+ walls) and (b) the walls deviated from X-direction for about 30 degrees (X+30 walls). It was shown that the X+30 walls were essentially faster than the Y+ ones. The jump-like domain wall motion caused by domain merging was revealed. The domain shape stability effect representing the fast restoration of the rhombus shape just after merging of small isolated rhombus was demonstrated. The dependence of the wall motion velocity on its orientation has been measured. The model of domain growth by generation of elementary steps and kink motion was presented. The revealed polarization reversal induced by chemical etching was attributed to action of the residual depolarization field appeared after partial removing of the screening charge layer.