Brillouin light scattering and second harmonic generation in barium strontium niobate films.

Temperature dependences of Brillouin light scattering spectra from Ba_0.5Sr_0.5 Nb₂O₆ (SBN 50) film were obtained. The deviations of the Brillouin shift dependence from linear near ferroelectric phase transition are due to electric fields in the local regions with symmetry breaking. A maximum of Brillouin line width is more than twice of the corresponding width in a bulk crystal of the same composition. This broadening is attributed to the confinement of the acoustic phonons. Optical second harmonic generation measurements (SHG) showed that the transition from the polar to the nonpolar phase occurred at a temperature characteristic of SBN-50. [ABSTRACT FROM AUTHOR]