POLARIZATION REVERSAL KINETICS WITH CONDUCTING DOMAIN WALLS: APPLICATION TO LITHIUM NIOBATE CRYSTALS
E. V. Podivilov1, N. G. Masnev2, B. I. Sturman1
1Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Russia
Keywords: domain wall conductivity, domain reversal, domain formation energy, reversal kinetics, nucleation, coalescence, lithium niobate
Abstract
We develop a theory of the ferroelectric polarization reversal taking into account conduction of domain walls. The case of capacitor geometry is considered as applied to lithium niobate. We show that the field dependence of the domain nucleation rate obeys the law exp(-En/E ), where E is the applied field and En ≈ 102 kV/mm is the characteristic field controlling the domain nucleation process. For the critical domains, the longitudinal size l*c strongly exceeds the transversal size 2l*a ≈ 1 nm. We formulate consistently a kinetic model of the field-induced polarization reversal. It includes not only random nucleation events but also the subsequent elementary events of the lateral growth obeying the Merz law exp(-El/E ) with the field El = En/3√3 controlled by the crystal symmetry. Numerical simulations show distinct stages of the domain nucleation, lateral growth, and coalescence. In accordance with experiment, the polarization switching time obeys the law exp( E*/E ) with E* = (En + 2El)/3, while the hysteresis loops show a standard behavior with the coercive field Ec = (3-5) kV/mm weakly dependent on the field ramping period.
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