PHENOMENOLOGICAL MODEL OF ELASTIC DISTORTIONS NEAR THE SPIN-PEIERLS TRANSITION IN CUGEO3

A phenomenological model of the Landau type forms the basis for a stud y of elastic distortions near the spin-Peierls transition T-c in CuGeO 3. The atomic displacements proposed by Hirota et al. [Phys. Rev. Lett . 73, 736 (1994)] are accounted for by the model which includes linear coupling between Cu and O distortions. Cu displacements are seen to b e responsible for anomalies in the elastic properties at T-c, whereas incipient O distortions give rise to temperature dependence below T-c. A discussion of possible critical behavior is also made.