Mesoscopic mechanism of the domain wall interaction with elastic defects in uniaxial ferroelectrics

The role of elastic defects on the kinetics of 180° uncharged ferroelectric domain wall motion is explored using continuum time-dependent Landau-Ginzburg-Devonshire equation with elastic dipole coupling. In one dimensional case, ripples, steps, and oscillations of the domain wall velocity appear due to the wall-defect interactions. While the defects do not affect the limiting-wall velocity vs. field dependence, they result in the minimal threshold field required to activate the wall motions. The analytical expressions for the threshold field are derived and the latter is shown to be much smaller than the thermodynamic coercive field. The threshold field is linearly proportional to the concentration of defects and non-monotonically depends on the average distance between them. The obtained results provide the insight into the mesoscopic mechanism of the domain wall pinning by elastic defects in ferroelectrics.