Evidence for Atomic Hopping of Fe in Perfectly Icosahedral AlfeCu Quasicrystals by $^{\bf 57}$Fe Mössbauer Spectroscopy

By $^{57}$Fe Mössbauer spectroscopy in a special experimental set-up we have shown the existence of Fe atomic jumps in Al$_{62}$Fe$_{25.5}$Cu$_{12.5}$ perfect icosahedral quasicrystals. The (preliminary) results indicate that at 790 $^{\circ}$C 20% of the Fe atoms are jumping at a time scale corresponding to 4 $\mu{\rm e}$V