Brillouin scattering studies of ferroic [NH2(CH3)(2)](3)Sb2Cl9 (DMACA)

High resolution Brillouin spectroscopy has been used to study the elastic p roperties of ferroic (i.e. ferroelectric and ferroelastic) [NH2(CH3)(2)](3) Sb2Cl9, otherwise known as DMACA. The experiments covered the temperature r ange from 170 to 300 K, and included the ferroelectric phase transition at about 240 K. The temperature dependence of Brillouin modes has been observe d for the longitudinal phonons propagating in the four directions [100], [0 10], [101] and [111]. The relaxation times of the order parameter were dete rmined and different types of coupling between polarization and strain are discussed.