Sideways dynamics of ferroelectric domain walls

Abstract

Characteristic features of the sideways motion of domain walls in ferroelectrics are considered. The proposed model for calculating the mobility of domain walls for this type of motion is based on the approaches developed by D. G. Sannikov and M. A. Collins et al. We examine the dynamics of domain walls in the vicinity of second-order phase transitions. The calculated domain wall mobility is in agreement with experiment in Pb 5Ge 3O 11, Pb 5− x Ba x Ge 3O 11, Rochelle salt, gadolinium molybdate, terbium molybdate, triglycine sulphate, and barium titanate. It is shown that the velocity of domain walls is proportional to the difference between the applied field and a threshold field. Good agreement with experiments in a number of ferromagnets and ferroelectrics is obtained in this aspect. The coupling of the spontaneous polarization to the strain is shown to induce propagation of solitary stress waves during the domain wall motion in ferroelectrics. We analyse some properties of stress wave propagation within the framework of the suggested model as well the elastic, electrostrictive and piezoelectric effects on the domain wall motion. The contribution of inertia to the velocity of domain walls is calculated. The domain wall mass for 180° walls in barium titanate estimated in the framework of the model is in accordance with its known value. Magnetic-field-induced motion of ferroelectric domain walls is considered. The finite-size effect on the mobility of domain walls is calculated. The mobility exhibits a critical increase when the sample thickness decreases. This behaviour is similar to the temperature growth of the mobility in the vicinity of the second-order phase transition temperature obtained in this model.