Regensburg 1998 – wissenschaftliches Programm

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M: Metallphysik

M 25: Postersitzung, gemeinsam mit AM,DS,DF,TT,SY B

M 25.30: Poster

Donnerstag, 26. März 1998, 15:10–19:10, A (Sammelgeb"aude)

The vibrational DOS of AlCuFe quasicrystals — •R.A. Brand¹, G. Coddens², and Y. Calvayrac³ — ¹Angewandte Physik, G-M-Universität GH Duisburg — ²Laboratoire Leon Brillouin CEA F-91191 Gif-sur-Yvette France Saclay — ³C.E.C.M./C.N.R.S., Vitry France

The vibrational DOS of Al₆₂Cu_25.5⁵⁷Fe_12.5 has been measured using inelastic nuclear resonant scattering on the ID18 beamline at ESRF. We have found a DOS with significant differences to that found by inelastic neutron scattering. The high-frequency modes are reduced, showing that these modes measured in inelastic neutron scattering are related to optical "phonons" involving mainly the lighter aluminium atoms. The low-energy side shows a nominal quadratic behaviour, but with a significant deviation in the range of 10 to 15 meV indicating low frequency optical modes. We also present some evidence for the existence of similar modes in the 1-4 meV region that might help in solving the discrepancy between inelastic neutron scattering and specific heat results in quasicrystals because such modes could have a structure factor that makes it hard to observe them by coherent inelastic neutron scattering.

Supported by the DFG Schwerpunkt Quasikristalle