First-Principles Study in New Hf2CoZ (Z = B, C, Al, Si, Ga, Ge, In, Sn, Tl, and Pb) Heusler Alloys

The full-potential linearized augmented plane wave method within density functional theory was used to investigate the electronic structures, magnetic properties, and half-metallicity in Hf2CoZ (Z = B,C, Al, Si, Ga, Ge, In, Sn, Tl, and Pb) alloys with AlCu2Mn- and CuHg2Ti-type structures. The AlCu2Mn-type structure is energetically favorable than the CuHg2Ti-type structure for all compounds. Hf2CoGa, Hf2CoAl, Hf2CoIn, Hf2CoTl, and Hf2CoSn compounds in the CuHg2Ti-type structure were half-metallic ferromagnets. The d-d and covalent hybridizations between transition metals Hf and Co were effective in the formation of minority band gap. The total magnetic moments of half-metallic Hf2CoZ (Z = Al, Ga, In, Sn, and Tl) compounds in the CuHg2Ti-type structure obeyed the Slater–Pauling rule (Mtot = Ztot − 18). Hf2CoIn and Hf2CoTl compounds were half-metals in relatively wide ranges of lattice constants which indicates that they can be promising and interesting candidates for spintronic devices.