DIFFUSION-LIKE MOTION OF THE MODULATION WAVE IN STRUCTURALLY INCOMMENSURATE SYSTEMS - A NQR STUDY

35Cl NQR measurements of the spin-echo decay in pure Rb2ZnCl4 exhibit an exponential t3 diffusional time dependence, which is the first clear evidence for the existence of slow random-walk-type motion of the incommensurate modulation wave close to the transition temperature TI. This phenomenon can be described by an effective diffusion constant Df in a reduced real space, which is settled as the projection of the direct space onto 14 the period length of the modulation wave. The onset of the incommensurate phase is accompanied by nonzero Df values, which rapidly decrease on going away from TI. © 1995 The American Physical Society.