Thermal, structural and magnetic properties of icosahedral Al₈₆Cr₈Fe₆ alloy

Abstract

Icosahedral alloy Al₈₆Cr₈Fe₆ and its crystallization products have been studied with X-ray diffraction, differential scanning calorimetry, ⁵⁷Fe Mössbauer spectroscopy, and magnetic susceptibility methods. The presence of a multiplicity of Fe sites is demonstrated, and this is interpreted as evidence of intrinsic disorder characteristic of icosahedral alloys. The analysis of the Mössbauer spectra of icosahedral alloys in terms of two doublets is shown to be methodologically incorrect, and consequently the basis of the so-called two-site model is unfounded. The crystallization products of the studied icosahedral alloy are Al₁₃Fe₄ and A1₁₃Cr_2-xFe _x- A small magnetic moment is present both in the icosahedral sample and in its crystallization products. The origin of the magnetic moment in icosahedral alloys is discussed in view of recent theoretical and experimental advances in the understanding of the electronic structure of these alloys.