Brillouin scattering in Na_1/2Bi_1/2TiO₃

Abstract

Measurements of Brillouin scattering in single crystal Na_1/2Bi_1/2TiO₃ are reported from 50 to 900 K which covers a cubic-tetragonal-trigonal succession of phase transitions, ending in a ferroelectric state. An extended dip in the hypersonic sound velocity and an extended maximum in the hypersonic damping were found with the extreme in the internansition region. These anomalies are connected with a response of mixed fluctuations. The Brillouin spectra background confirms the existence of a central peak in light scattering whose intensity increases drastically in the same internansition region.