Abstract
Using a Landau-Khalatnikov approach we calculate the temperature dependence of the dielectric constant and of the coupled normal modes in incommensurate phase transitions such as that displayed by BaMn. It is assumed that the phase mode is relaxational in the incommensurate phase and satisfies a Debye relaxation equation. Two results of interest are generated: first, the temperature dependence of the inverse relaxation time is given by , in agreement with experimental results for both BaMn and Na; and second, a new relationship between the dynamical parameters and and the temperature width of stability for the incommensurate phase, is derived: , where is a numerical constant of order 1.0 to 6.0 in the anisotropic case. Using experimental values of Hz and Hz for BaMn, we calculate K, in good agreement with the recent measurement of 8.2 K by Scott, Habbal, and Hidaka; similar estimates for Na predict a large incommensurate temperature region, which is also in good accord with experiment.
- Received 29 October 1979
DOI:https://doi.org/10.1103/PhysRevB.24.2711
©1981 American Physical Society