Electronic and atomic disorder in icosahedral AlPdRe

Abstract

Relations between electronic and atomic disorder of i-AlPdRe have been investigated bystudies of neutron irradiated and annealed samples. The advantage with this technique isthat a single sample can be monitored over a significant range of varying electronicproperties, without concern for any influence of varying impurities. X-ray diffraction, theelectrical resistivity and its temperature dependence, and the magnetoresistance arestudied. The results show that annealings of an irradiated sample lead to improvement ofthe atomic order, as reflected in increased intensities of the x-ray diffraction peaks,while electronic properties change in the direction of increasing electronic disordertowards a metal–insulator transition. The observed relation in quasicrystals thatimproved atomic structure is associated with stronger anomalies in transportproperties is thus also seen in i-AlPdRe. In particular, the variation of the diffusionconstant in the region of small values of the resistivity is found to be similarfor annealed polygrain samples and for single grain samples with varying Pdconcentration, as evaluated from literature data, indicating a similar developmentof electronic disorder in both sets of samples. However, the problem remainsas to why the resistivity is small in single grain samples which are atomicallywell-ordered. The possibility of a strong sensitivity to concentration differences is pointedout.