Self-diffusion in icosahedral Al72.4Pd20.5Mn7.1 and phason percolation at low temperatures studied by Al-27 NMR

Aluminum self-diffusion in a monodomain icosahedral quasicrystal Al72.4Pd20 .5Mn7.1 has been studied at temperatures between 4 and 400 K by Al-27 NMR m easurements of the decay of transverse nuclear spin magnetization in a spat ially inhomogeneous electric field gradient. Temperature dependence of the renormalized diffusion constant can be explained in the framework of the Ka lugin-Katz phason-assisted diffusion model where the atomic jumps occur as a result of the presence of matching-rules violation defects. The observed self-diffusion process resembles a percolation transition with the percolat ion threshold at 72 K. [S0031-9007(98)08203-9].