Barkhausen pulses caused by domain merging in congruent lithium niobate

摘要

The analysis of the shapes of Barkhausen pulses (BPs) was used for the detailed characterization of the domain merging process in congruent lithium niobate LiNbO_3 (CLN) crystals. The BPs in ferroelectrics manifest themselves as the sharp peaks in a switching current during polarization reversal by the application of a constant or slow-varying external electric field. Three mechanisms of the BPs were previously proposed: domain nucleation, interaction of the domain walls with the pinning centers, and domain merging. We have revealed the domination of the domain merging mechanism for the generation of the BPs in CLN and classified the scenarios of domain structure evolution after merging in terms of the appearance and transformation of short-lived fast and superfast domain walls. We have shown that the input of merging events reaches 80% of the whole switching process. Two revealed types of BPs corresponding to the merging events considerably differ by duration and shape, thus opening the way for solution of the inverse problem-extracting the quantitative information about the domain kinetics by the analysis of the BPs. This analysis allows extracting the velocities of the fast and superfast walls and provides the possibility to go beyond the temporal resolution of the in situ imaging system in studying the superfast domain wall motion. The proposed analysis is applicable for the faceted growth of polygonal domains in any ferroelectric. It is necessary to point out that the analysis of the BPs allowed characterizing the main part of the domain evolution process in CLN as the fast domain transformations after merging prevail during the polarization reversal.