BRILLOUIN-SCATTERING STUDY OF THE ELASTIC-CONSTANTS OF PHENOTHIAZINE THROUGH THE PHASE-TRANSITION - COMMENT

In the paper of Sartwell and Eckhardt (denoted as SE) [Phys. Rev. B 48 , 12438 (1993)] controversial results about ferroelasticity of phenoth iazine are presented. These authors cast some doubts on the validity o f our measurements [Ecolivet et al., Phys. Rev. B 44, 4185 (1991)]. We detail here the method we used and its advantages and we point out so me questionable results and assertions of the former paper. In particu lar, we present a comparison of the diagonal elastic constants of phen othiazine obtained from different techniques, which have been ignored or misused in the SE paper. The results here, rather, show a convergen ce against the results of the SE paper. Finally, the problem of the qu ality of the crystals is addressed.