On the origin of the giant magnetic moment of the Al-Mn quasicrystals

¹ Bauman Moscow State Technical University, Department of Machinery Technology, Moscow, Russia
² Moscow State University, Department of Physics, Moscow, Russia

Abstract

Ab initio calculations of magnetic moments for icosahedral clusters contained in crystal structures Al₁₀Mn₃, Al₅Co₂, Al₁₇Mn₄ (Al₁₃Cr₄Si₄-type) fulfilled in the framework of Density Functional Theory. The AlMn cluster having the trigonal D_3h symmetry with the triangle of Mn ions in the interior has the moment being equal to three magnetic moments of a single manganese ion (4.4 μ_B), the moment of the tetrahedral T_d cluster with the Mn tetrahedron in the interior is equal approximately to twelve magnetic moments of the single manganese ion (15.5 μ_B). The magnetic moment of icosahedral Al-Co clusters having the same configuration is equal to zero. The magnetic moments of the rod assembled from the icosahedral clusters with the sequence T_d D_3h - T_d was found to be 20.5 μ_B. This value permits to explain the giant magnetic moment of icosahedral and decagonal Al-Mn quasicrystals and gives the indirect evidence to the hierarchical model of the quasicrystals structure proposed by the authors recently. An arrangement of magnetic moment carriers in the interior of the aluminum shell of icosahedral clusters permits to suggest the interaction between contacting manganese ions as the main origin of the giant magnetic moment of the Al-Mn quasicrystals.