Slowness surfaces study of the ferroelastic phase transition of LiCsSO4 crystal
The method of slowness surface is used to study the ferroelastic phase transition of LiCsSO4. The slowness surfaces of the crystal have been plotted between 202K and 293K. The direction of the maximum slowness is on the XZ plane and the angle of it and X axis is -49.5 degree when temperature is above 206K. At 206K, the direction of the maximum slowness is along X axis. As the temperature decreases from 206K to 202K, the direction of the maximum slowness doesn't change anymore but the slowness surfaces change dramatically. According to the soft mode theory and the elastic constitutive relations, we obtained that LiCsSO4 crystal is in the same symmetry between 202K and 206K.
Acoustic study of the ferroelastic phase transition in LiCsSO4 crystal
The paper reports on an acoustic study of the temperature dependences of the ultrasonic-wave velocity and attenuation in a LiCsSO4 crystal within the 190–295 K temperature region, which includes the interval of the pseudoproper second-order ferroelastic phase transition (202 K). The velocity of the transverse xy acoustic mode is found to decrease by more than six times at the phase transition. The possibility of performing ultrasonic studies both in the region of the ferroelastic phase transition temperature and below it is demonstrated. The results are treated in terms of Landau’s theory. Waves not associated with the soft mode are shown to exhibit anomalies which are supposedly due to an intermediate phase, whose existence was suggested in a number of publications.
Electron-paramagnetic-resonance study of Cu2+- and Mn2+-doped LiCsSO4 single crystals: LiCsSO4 phase transitions.
EPR studies on Mn 2+ -doped LiCsSO 4 single crystals were performed in the temperature range 3.8-301 K, as well as on Cu 2+ -doped LiCsSO 4 single crystals at room temperature. At higher temperatures the crystals were found to consist of twin domains. There were detected twuo phase transitions, one of which occurs at 205 K, and the other one is spread over the temperature range 155-175 K. In addition, the occurrence of a third phase transition somewhere in the range 3.8-31 K has been confirmed by the present data. The values of the isotropic g factor and the hyperfine-interaction constant for Mn 2+ have been estimated at room temperature