Elastic properties of purified [N(CH3)4]2CuCl4 crystals near the ferroelastic lock-in transition
The 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.