Magnetic properties of Al-based icosahedral alloys

One of the fundamental questions which inas not been answered sufficiently well till today is whether a nonclassical symmetry such as an icosahedral one would induce any special and distinctive features in the physical properties of the systems, Most theoretical investigations indicate that there are unique features in the electronic structure on account of icosahedral symmetry which could for example, influence the magnetic properties significantly. Experimental studies, particularly, on Al-based icosahedral alloys, have shown a large variation in magnetic properties ranging from diamagnetic to Curie like and Pauli paramagnetism on one hand and ferromagnetic and spill glass like behaviour on the other. In the present article, we will concentrate on some aspects of moment formation and variation in magnetic properties in AI-Mn based icosahedral systems and their dependence on the method of preparation which presumably controls and introduces the variable disorder. We will also try to answer some pertinent questions related to magnetism in icosahedral systems such as extent and origin of moment formation,existence of magnetic and nonmagnetic Mn sites and distribution of interatomic distances responsible for variation in magnetic properties.