Domain Wall Dynamics in Ferroelastic Crystals

Results of ultra-low-frequency dynamic mechanical analysis (Hz-region) measurements of the mixed fluoroperovskite crystals KMn(1-x)CaxF(3) (x <= 0.018) are presented in a wide temperature range including the regions of phase transitions. At low frequencies (0.1 Hz-50 Hz) a giant elastic softening (superelasticity) due to domain wall motion was found in the mixed system quite similar to that observed recently in the isostructural SrTiO3. Moreover, the low frequency elastic behaviour in KMn(1-x)CaxF(3) bears some important new features as compared to SrTiO3. For the first time we have measured the freezing of domain wall movement in a certain range of concentration of Ca2+ ions (x = 0.003).