Local order of icosahedral quasicrystals studied by Moessbauer spectroscopy

Thermodynamically stable Al-Cu-Fe and Fe-doped ferromagnetic Al-Cu-Ge-Mn icosahedral quasicrystals were studied by 57Fe transmission Moessbauer spectroscopy and X-ray diffraction experiments. The Al65Cu20Fe15 quasicrystalline alloy was subjected to mechanical grinding for up to 800 hours in a ball mill. In the early stage of grinding, the presence was revealed of an amorphous phase which co-existed with the quasicrystalline phase. Moessbauer measurements were performed on the icosahedral Al40Cu10-xGe25Mn25Fex quasicrystal (x ranging from 0.1 to 3) in the temperature range from 10 to 548 K. It was found that a magnetic transition occurs at about 30 K which is far below the Tc reported in the literature. It is concluded that the Al-Ge-Mn ferromagnet present in the samples does not affect the magnetic transition observed and that the transition is an intrinsic property of the Al-Cu-Ge-Mn host alloy. (author) 10 figs., 15 refs