Phason-dynamics studied by quasielastic mossbauer scattering in i-Al-Cu-Fe quasicrystals

Quasicrystals can show a new type of localised defect termed a 'phason'. At high temperature, these defects become mobile and lead to short-ranged atomic motion without involving vacancies. Cu in i-Al-Cu-Fe is involved in such phason jump process at high temperatures T on a time scale tau of h/250 mu eV. Surprisingly, tau (Cu) was found independent of the temperature, indicating a type of 'assisted' jump process. In order to investigate the iron dynamics in this system, we have studied i-Al62Cu25.5 Fe-57(12.5) using quasielastic Mossbauer spectroscopy for T less than or equal to 1100 K. We find a temperature-dependent iron phason jump process with tau (Fe) typically two orders of magnitude slower than copper. (C) 2000 Elsevier Science B.V. All rights reserved.