Brillouin Scattering Study of the Ferroelastic Phase Transition of BiVO₄

Abstract

The elastic instability in the ferroelastic phase transition of BiVO₄ was investigated by the observation of the Brillouin scattering spectra as a function of temperature around the transition temperature. From the temperature dependence of the observed spectra in two different scattering geometries it turns out clear that the softening of elastic stifiness constant c₁₁−c₁₂, not of c₆₆, causes the ferroelastic transition. The elastic softening is discussed in connection with the domain structure.