Domain Walls in Some Ferroelectrics with Incommensurate Phases

Abstract

The fundamental features of ferroelectric domain walls are studied on the basis of the model thermodynamic potential applicable to ferroelectrics, such as SC(NH₂)₂, which have incommensurate phases. The model, when discretized, describes kinks formed in a chain of atoms sitting on a substrate double minimum potential, where the nearest neighbor interaction is of the antiferro-type while the next nearest neighbor one is of the ferro-type. The spatial variation of an order parameter within the walls, the wall energy and the activation energy were calculated as functions of model parameters. The situation that the incommensurate phase is stabilized with decreasing temperatures, prior to the commensurate phase, is reflected in a special feature of spatial variation of the order parameter.