Electronic Structures, Magnetic Properties and Half-Metallicity of Heusler Compounds Hf 2 VZ ( Z = Ga, In, Tl, Si, Ge, Sn and Pb): First-Principle Calculations

We investigate the electronic structures, magnetic properties and half-metallicity of Heusler compounds Hf2VZ (Z = Ga, In, Tl, Si, Ge, Sn and Pb) with Hg2CuTi-type structure by using the first-principle calculations based on density-functional theory. It is found that the equilibrium lattice constants of Hf2VZ (Z = Ga, In, Tl, Si, Ge, Sn and Pb) compounds are 6.68, 6.88, 6.91, 6.57, 6.63, 6.85 and 6.94 A, respectively. Hf2VZ (Z = Ga, In, Tl, Si and Sn) compounds exhibit half-metallicity at their respective equilibrium lattice constants. Hf2VGe and Hf2VPb do not exhibit half-metallicity at their equilibrium lattice constants but can present the half-metallicity when the lattice constant decreases to 6.51 and 6.71 A, respectively. In case of the lattice thermal expansion, the half-metallicity can be kept in the range of 6.30∼ 7.27, 6.36∼ 7.80, 6.46∼ 7.35, 6.00∼ 6.70 and 6.10∼ 6.95 A (lattice constant) for Hf2VZ (Z = Ga, In, Tl, Si and Sn). Under the unaxial strain, the half-metallicity can still be kept for Hf2VZ (Z = Ga, In, Tl) when the lattice distortion is up to ± 10% (c/a) and be kept for Hf2VZ (Z = Si, Sn) when the lattice distortion is 0.88∼ 1.09, 0.91∼ 1.09 (c/a). For the Hf2VZ compounds with half-metallicity, the total magnetic moment is 2 μB when Z is the third main group elements and is 1 μB when Z is the fourth main group elements. The Hf2VZ compounds with half-metallicity obey the Slater-Pauling formula: Mt = 18 − Zt rule.