Critical behavior of acoustical waves in ferroelectric-ferroelastic phase of Tb2(MoO4)3

Abstract
Ultrasonic measurements are analysed in the low-temperature phase of TMO monodomain. A 0.50 (± 0.03) critical index for elastic constants C11 and C22, and a 1.45 (± 0.05) critical index for α 11 and α22 attenuations of longitudinal waves along α and b axis were found. These results can be explained on the hypothesis of an isotropic softmode dispersion curve by a coupling linear in strain, and quadratic in order parameter. The equality α11 = α 22 which is found is explained by symmetry