Soft Optic Modes in Barium Titanate

Abstract

Phonon dispersion relations of BaTi${\mathrm{O}}_{3}$ have been measured in the cubic phase by the inelastic neutron scattering technique. The energy of the soft mode, consistent with Cochran's theory, decreases with temperature to 0.8 meV at 230\ifmmode^\circ\else\textdegree\fi{}C.