Acoustic—Soft-Optic Mode Interactions in Ferroelectric BaTiO3

Abstract

The Raman and Brillouin spectra of tetragonal ferroelectric BaTi${\mathrm{O}}_3$ have been studied between 7 and 133°C. In addition to providing the temperature dependences of the sound velocity and absorption, these spectra exhibit several anomalies which are quantitatively attributable to the interaction between acoustic phonons and the soft optic mode responsible for the ferroelectric phase transition in BaTi${\mathrm{O}}_3$.