Comment on ‘‘Direct observation of relaxation modes inKNbO3andBaTiO3using inelastic light scattering’’

Abstract

The inelastic light scattering data, recently reported by Sokoloff, Chase, and Rytz [Phys. Rev. B 38, 597 (1988)] in orthorhombic ${\mathrm{KNbO}}_3$, are not in agreement with our previous investigations. We show that, contrary to our interpretation, their results are not able to solve the long-standing controversies about the mechanism of the phase transitions in ${\mathrm{KNbO}}_3$. We point out the importance of the coexistence of a relaxation mode and a soft phonon along the same axis.