Magnetic properties for the transition-metal aluminides XAl2 (X = V, Cr, Mn, and Co): A first-principles study

We have investigated the magnetic properties of the transition-metal aluminides XAl2 (X = V, Cr, Mn, and Co) in the MoSi2 type structure by first-principles calculations. Considering the electron–electron correlations, we predict VAl2 and CoAl2 to be half-metallic ferromagnets. The transition-metal aluminides alloys, such as (CrFe)0.5Al2 and (MnFe)0.5Al2, obtained by substitution of half of the transition-metal atoms by other transition-metal atoms are nearly half-metals with high spin polarizations at the Fermi level. The density of states of these materials exhibit the features of a spin-up gap or a spin-down gap at the Fermi level. The total magnetic moments for these half-metals are integers and obey the Slater–Pauling rule of scaling linearly with the total number of the valence electrons in the unit cell in the form of Mt = Nt − 28 (or Mt = 28 − Nt). CrAl2 and MnAl2 are antiferromagnets, but their ferromagnetic spin configurations also show half-metallicity.