Browsing by Author "Warhanek, Hans"
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- ItemElastic properties of purified [N(CH3)4]2CuCl4 crystals near the ferroelastic lock-in transition(1996) Müller, Volkmar; Fuith, Armin H.; Fousek, Jan; Warhanek, Hans; Beige, HorstThe low frequency elastic properties of ferroelastic [N(CH3)4]2CuCl4 crystals are investigated by dynamical mechanical analysis in the vicinity of the incommensurate-commensurate phase transition. We show for the first time, that the anomaly of the elastic compliance coefficient S55, even of purified crystals, is accompanied by typical nonequilibrium phenomena such as isothermal relaxations. The S55(T) anomaly was not significantly enhanced by the purification treatment. We conclude, that extended defects induced during crystal growth have a decisive influence on the elastic properties of [N(CH3)4]2CuCl4.
- ItemSpontaneous strain in ferroelastic incommensurate [N(CH3)4]2CuCl4 crystals(1997) Müller, Volkmar; Fuith, Armin H.; Fousek, Jan; Warhanek, Hans; Beige, HorstThe temperature dependence of spontaneous strain is investigated in the ferroelastic lock-in phase of [N(CHs),&CuCIi crystals by thermal mechanical analysis. The critical index of the order parameter modulus is found to be j3 =0.33. Considerable wall displacements have been detected for shear stress as small as a, =2.4kPa which indicates that the mechanical pinning energy is extremely small. 0 1997 Published by Elsevier Science Ltd