On the Dependence of the Switching Time of Barium Titanate Crystals on Their Thickness

The dependence of switching rate on the crystal thickness has been measured by Merz and explained by him in terms of a surface layer which has a low dielectric constant, and is about 10−4 cm thick. While not explicitly stated in Merz' original arguments, the layer must have a reversible polarization. If a layer without a reversible polarization is assumed, instead, and the discontinuity of the normal component of polarization at the interface between the layer and the bulk is taken into account, then a much thinner layer (∼1 atomic thickness) will explain the thickness dependence. This layer can be taken to be very lossy, so that it has a relaxation time (for the disappearance of electric fields) short compared to the switching time, and yet the layer will still be completely effective in slowing down domain wall motion.