A comparison of the57Fe EFG properties in the crystalline and quasicrystalline phases of the Al−Si−Mn system

Abstract

We present here the determination of the distributionP(q) of the electric field gradient in Fe-doped Al−Si−Mn icosahedral and decagognal quasicrystals and in the related crystalline phases, using in-field Mossbauer effect spectroscopy. The distributionP(q) for the quasicrystalline compounds shows a bimodal, nearly symmetric form withP(0)≃0 and equal averages over positive and negativeq=1/2eQVzz:−〈q−〉∼-〈q+〉 and equal standard derivations: σ−≃σ+. The results for the majority sign of the distributionP(q) will be compared to the results for the cubic, hexagonal and orthorhombic compounds. The results show that there are similarities in the local order between the icosahedral quasicrystalline phase and the hexagonal phase. No evidence is found for a two-site model which as recently been proposed by other authors.