Motion of fast and superfast domain walls during polarization reversal in crystals of lithium niobate family

• Published in: Journal of Advanced Dielectrics
• Main Authors: I. A. Kipenko, A. R. Akhmatkhanov, V. Ya. Shur
• Format: Article
• Language: English
• Published: World Scientific Publishing 2025-10-01
• Subjects: Kinetic Wulff plot; domain wall motion; uniaxial ferroelectrics; domain wall orientation
• Online Access: https://www.worldscientific.com/doi/10.1142/S2010135X2550002X
• ISSN: 2010-135X; 2010-1368

We have studied the kinetics of domain walls in lithium niobate (LN) crystals with stoichiometric and magnesium oxide doped compositions. We have analyzed the kinetic maps of the switching process to separate the main types of domain walls, their relative input and their field- and orientation-velocity dependence. All obtained domain walls were divided into three groups characterized by orientations and velocity: “slow walls”, “fast walls” and “superfast walls”. The dominant role of the fast and superfast walls in the switching process in the whole field range for studied crystals was revealed. The measured kinetic Wulff plot demonstrates the six-fold symmetry for the slow walls and three-fold symmetry for fast and superfast walls. The measured field dependencies of slow, fast and superfast domain wall velocities in all studied crystals were analyzed using two alternative approaches by linear and exponential fittings. The obtained wall orientations were attributed to the wall structure, characterized by averaged step length (kink concentration). It is shown that the mobilities of all types of walls in stoichiometric LN are several orders of magnitude higher than in doped crystals. In contrast, the threshold fields demonstrate a pronounced dependence on composition, which was attributed to dependence on the deviation from the stoichiometry and the healing role of the doping by MgO. Detailed studies of the kinetics of domain walls of various orientations in the main representatives of the LN family are important for further development of domain engineering methods for creation of the nonlinear optical frequency conversion devices.