Surface effects on phase transitions in ferroelectrics and antiferroelectrics

The phenomenological theory describing the change of the local order parameter in the vicinity of free surfaces of ferroelectrics and anti ferroelectrics is reviewed. In the latter systems, particular drastic effects occur near the second order phase transition between the ordered and the disordered state, where new critical exponents need to be introduced to describe the critical behavior. In contrast, depolarizing field effects in ferroelectrics reduce the deviation of this local polarization from its bulk value. Predictions for the polarization profile across a (strictly insulating) thin ferroelectric plate between metallic electrodes are made. A comparison of these results is made to surface effects on phase transitions in other systems, such as magnets or ordering alloys. The experimental observability of these theoretical predictions is briefly di scussed.