Optical study of the transition of doped potassium tantalate

We report on recent findings obtained through Raman scattering, second harmonic generation and linear birefringence on the polar phase of doped KTaO3. At low temperature, the polar coherence length ranges from a few nanometers to 20 nm for 1.6% and 6% Li doping, respectively and shows no criticality. Comparable figures are found for the case of 12% Na doping. The evolution of low energy Raman spectra and the behaviour under a poling field provides further evidence of phenomena which limit the growth and cooperative ordering of polar microregions.