Band-gap and Slater-Pauling rule in half-metallic Ti2-based Heusler alloys: A first-principles study

Half-metals, which show 100% spin polarization at the Fermi level, have potential applications in spintronics. We investigated the half-metallicity of full-Heusler Ti2YAl (Y = V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) alloys with an Hg2CuTi-type structure by means of the all-electron full-potential linearized augmented plane-wave method within the generalized gradient approximation. The Ti2MnAl alloy is found to be a half-metallic antiferromagnet, and the Ti2YAl (Y = Fe, Co, and Ni) alloys are half-metallic ferrimagnets, whereas the Ti2YAl (Y = V, Cr, Cu, and Zn) alloys are conventional ferromagnets. Total magnetic moments (M-t) of the Ti2YAl (Y = Mn, Fe, Co, and Ni) alloys are calculated to be integers and linearly scaled with the total number of valence electrons (Z(t)) by M-t = Z(t)-18. Band-gaps are demonstrated to be mainly determined by the bonding t(2) and antibonding t(2)* states created from the hybridizations of the d states between the Ti(A)-Ti(B) coupling and Y (Y = Mn, Fe, Co, and Ni) atom. (C) 2012 Elsevier B.V. All rights reserved.