Raman study of phase transitions in rare earth vanadates

The phase transitions in DyVO₄ at about 14K and in TbVO₄ at about 33K have been investigated by Raman scattering. The E_g phonons are split below the transition temperature but the singlet phonon modes are not appreciably affected. No soft phonon mode is observed but large changes are seen in the low lying electronic levels. These results appear to be a consequence of a cooperative Jahn-Teller effect.