NMR methods for detection of slow atomic motions in quasicrystals

Abstract We present NMR techniques for the detection of slow, low-activation-energy, diffusive atomic motion in quasicrystals, within the frequency window from several 10 kHz down to the milli-Hz region. The techniques involve two-dimensional exchange NMR experiments, the diffusion-induced decay of the Hahn spin echo in an inhomogeneous electric field gradient and the Carr–Purcell echo-train experiment. These techniques were applied to the icosahedral AlPdRe and decagonal AlNiCo quasicrystals and to the ‘vacancy-ordered’ periodic AlCuNi phase. In all compounds we detected slow, low-activation-energy, diffusive atomic jumps that persist down to low and very low temperatures. Identical motions were detected also in the periodic AlCuNi alloy, suggesting that the observed atomic dynamics are not quasicrystal-specific.