Optical second harmonic generation studies of the ferroelectric phase transition in new materials exhibiting cooperative dipole effect

Summary form only given. New ferroelectric materials of M/sub 2/P/sub 2/X/sub 6/-family, which piezo-, pyroelectric and dielectric properties are promising for applications are studied by means of optical second harmonic generation (SHG) in the vicinity of phase transition temperature T/sub c/. The motivation for the studies of ferroelectrics by the SHG based method is two-fold: to probe their intrinsic nonlinear optical properties and to use nonlinear optical techniques for probing the symmetry and structure of ferroelectric materials. Moreover, the SHG probe are much more potential to study the behavior of symmetry and structure parameters and electronic properties of ferroelectrics in the vicinity of phase transitions.