First-principles study of half-metallic properties of the Heusler alloy Ti2CoGe

First-principles calculations have been performed on the electronic structures and magnetic properties of a new Ti₂Co-based full-Heusler alloy Ti₂CoGe. The calculations predict the Ti₂CoGe is a half-metallic ferromagnet at the equilibrium lattice constant with the minority-spin energy gap of 0.60 eV. It is found that the total magnetic moment (M_t) and the number of valence electrons (Z_t) in Ti₂CoGe obey a new Slater–Pauling (SP) rule of M_t=Z_t−18 and the rule also can be applied to other Ti₂Co-based half-metallic full-Heusler alloys. The Ti₂CoGe alloy keeps a 100% polarization at Fermi level and maintains the half-metallic character for lattice constants ranging between 6.05 and 6.67 Å.