Correlations in the electronic properties of AlCuFe quasicrystals and high-order approximates: 57Fe Mössbauer, and 27Al and 65Cu nuclear magnetic resonance studies

Abstract

We have investigated the local electronic properties and the atomic order in the Al100-x-yCuxFey, phases using 57Fe Mössbauer as well as 27AI and 65Cu nuclear magnetic resonance (NMR) spectroscopies. We have studied samples along the existence domains of the icosahedral quasicrystalline (i-) and the high-order approximant phases, given by two close-lying parallel lines in the concentration diagram. In addition, we have also studied a series of intermediate concentrations situated between these lines and retained in a metastable i-phase by quenching. It is found that the 57Fe Mössbauer centre shift (isomer shift) and quadrupole splitting are linearly correlated with 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 electronic shift follows this correlation. The results are discussed in terms of the hybridization of iron d states with the p and induced d states of Al. We have studied also a low-order cubic approximant phase containing Si as well as several non-approximant crystalline phases.