Regensburg 1998 – scientific programme

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M: Metallphysik

M 23: Quasikristalle I

M 23.6: Talk

Thursday, March 26, 1998, 12:10–12:30, H 33

Correlations in the electronic properties of AlCuFe quasicrystals and high-order approximants — •R.A. Brand¹, J. Voss¹, F. Hippert², and Y. Calvayrac³ — ¹Angewandte Physik, G-M-Universität GH Duisburg — ²Laboratoire de Physique des Solides, Université de Paris Sud, France — ³C.E.C.M./C.N.R.S., Vitry France

We investigated the local electronic properties and atomic order in Al_100−x−yCu_xFe_y phases using ⁵⁷Fe Mössbauer as well as ²⁷Al and ⁶⁵Cu NMR spectroscopies. It is found that the ⁵⁷Fe Mössbauer centre shift (isomer shift) and quadrupole splitting are linearly correlated to each other over the range of compositions and structures for all samples which reveals systematic changes in the orbital occupations on Fe atoms with composition. In addition, it is found that the ²⁷Al NMR average shift follows this correlation, demonstrating covalent bonding between Al sp-d-states and Fe sp-d-states. We have studied as well a low-order cubic approximant phase containing Si and several non-approximant phases: these results do not fall on the correlation line, indicating different atomic binding.

These results will be compared to Al, Cu and Fe EXAFS studies of the different phases.

Supported by the DFG Schwerpunktprogramm Quasikristalle