An anisotropic softening of the acoustic mode in the ferroelastic phase transition of LaNbO4 has been observed by the Brillouin scattering experiment. The transverse mode propagating along a direction deviated from the crystal axis by 23° in the flZ)-plane shows a complete softening at the transition temperature Tq. The direction is parallel or normal to the ferroelastic domain boundary as predicted by the phenomenological analysis of the phase transition from 4/m to 2/m symmetry. The temperature dependence of the elastic susceptibility is well described by the classical indices y=y'=1 in both phases, suggesting a typical proper ferroelastic transition.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)