Münster 1997 – wissenschaftliches Programm

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M: Metallphysik

M 6: Quasikristalle

M 6.6: Vortrag

Montag, 17. März 1997, 17:10–17:30, S 6

AlCuFe Quasicrystals: Local Electronic Properties of these new Industrial Materials — •R.A. Brand¹, J. Pelloth¹, F. Hippert², and Y. Calvayrac³ — ¹Angewandte Physik, Universität Duisburg, D-47048 Duisburg, Germany — ²Physique des Solides, Université de Paris Sud, F-91405 Orsay Cédex, France — ³C.E.C.M./C.N.R.S., 15 rue G. Urbain, F-94407 Vitry Cédex, France

We present room temperature ⁵⁷Fe Mössbauer isomer shift and electric field gradient (EFG), ²⁷Al and ⁶⁵Cu NMR average shift and EFG as well as Cu- and Fe-edge EXAFS studies in the Al_100−x−yCu_xFe_y icosahedral-quasicrystalline (i-) and crystalline phases. We have investigated the local electronic properties and atomic order along the existence domains of the quasicrystalline and approximant phases given by two close-lying parallel lines in the concentration diagram. It is found that the ⁵⁷Fe centre line shift and EFG as well as the ²⁷Al average shift are linearly correlated to each other over the range of compositions and structures. This correlation results from systematic changes in the orbital occupations on Fe and Al atoms with composition. We report as well on new EXAFS studies of these phases. We have investigated as well the new low-order cubic approximant phase containing Si. The results for this phase fall near to but not on the correlation line indicating small changes in the atomic binding as compared to the i- and high order approximant phases.