Depinning of the ferroelectric domain wall in congruent LiNbO₃

The high coercive field, E_c, of congruent LiNbO₃ can be reduced by doping with Mg or Zn atoms, or by increasing the temperature above a threshold value. The physical origin for this reduction is not currently understood. Here, density functional theory calculations illustrate the atomic origin of the change in the switching field of the congruent LiNbO₃. They show that the high E_c in the congruent LiNbO₃ is a result of niobium antisite atoms on the lithium sublattice, pinning the motion of the domain walls. Thus, the healing of antisites by diffusion can significantly reduce the coercive field. In addition, this work demonstrates that the migration of these niobium antisites can be enhanced by doping or by changing the temperature. Thus, the depinning process of the congruent LiNbO₃ is understood by the migration of the niobium antisite defect across the domain wall.