Half-metallicity and onsite Hubbard interaction on d-electronic states: a case study of Fe(2)NiZ (Z = Al, Ga, Si, Ge) Heusler systems

摘要

DFT-based structural optimisations of Fe(2)NiZ (Z = Al, Ga, Si, Ge) Heusler compounds confirm the stability of these alloys in F-43m phase. While defining the electronic structure, onsite Hubbard approximation scheme for exchange correlations predicted better results than the generalised gradient approximation. Calculated band structure and densities of states together with spin magnetic moments designate the half-metallic character of these alloys. Indirect band gaps, 1.2 eV for Fe2NiAl, 0.98 eV for Fe2NiGa, 1.3 eV for Fe2NiSi and 1.1 eV for Fe2NiGe in spin-down states are observed. The ferromagnetic spin moments amount to an integral value of 5 mu B for (Al, Ga) and 6 mu B for (Si, Ge) systems with a maximum contribution from transition metal atom (Fe). To forecast the possible turnout of the thermopower, Seebeck coefficients, electrical and thermal conductivities are calculated, which directly hints the thermoelectric response of these materials. This study creates a possibility of these alloys in thermoelectrics and spintronics.