Phason-dynamics studied by quasielastic mössbauer 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 τ of ℏ/250 μeV. Surprisingly, τCu 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 57Fe12.5 using quasielastic Mössbauer spectroscopy for T≤1100 K. We find a temperature-dependent iron phason jump process with τFe typically two orders of magnitude slower than copper.