Structural, electronic, and magnetic properties of 3d transition-metal aluminides with equiatomic composition.

Abstract

First-principles calculations have been performed to study the chemical bonding trends and the phase stability of 3[ital d] transition-metal (TM) aluminides with equiatomic composition. The physical mechanisms for ordering in both the [ital L]1[sub 0] and [ital B]2-type aluminides are presented. It is shown that the dominant factor for early TM aluminides is the directional bonding between the [ital d] orbitals of TM atoms, whereas for late TM aluminides, charge transfer and hybridization between Al [ital s] and [ital p] states, and TM [ital d] states play more important roles in the bonding mechanism and the properties of lattice defects. Our calculations also show the existence of a ferromagnetic phase for MnAl in the [ital L]1[sub 0] structure, which is stabilized by the formation of a magnetic moment on the Mn sites (with a value of 2.0 [mu][sub [ital B]]). The chemical trends in the structural stability and heats of formation of 3[ital d] TM aluminides are found to correlate well with the densities of states at the Fermi level.