Half-metallic p0-d half-Heusler alloys with stable structure in ferromagnetic state

Abstract

We investigate the structural, magnetic, thermodynamic, and mechanical stability of p0-d half-Heusler compounds composed of p0 = Li, Be, Na, Mg alkali and alkaline earth metals; 3d transition metals; and group V (pnicogens) & VI (chalcogens) sp atoms using the DFT based full-potential Wien2k package. Ferromagnetic, antiferromagnetic, and non-magnetic calculations are performed to ascertain the stable magnetic state. From 280 compounds under study, 16 of them show half-metallic properties in the minimum-energy half-Heusler phase at the optimized lattice constant. Calculations show that compounds are stable in the half-Heusler β-phase and the ferromagnetic state. The band structure and the density of states are obtained for both GGA and GGA + U exchange correlation approximations. Furthermore, in order to study the thermodynamic and the mechanical (dynamic) stability of the compounds, the formation energy, the hull distance, and the elastic constants of half-metallic compounds are calculated. The estimated coupling constants and Curie temperatures from Monte Carlo simulations show that these compounds preserve the ferromagnetic state and magnetic polarization at temperatures much higher than the room temperature and may well be suitable materials for spintronic applications. The phonon dispersion curve for NaVBi as the compound that has the highest Curie temperature among half-metallic compounds shows no imaginary frequencies and testifies to the dynamic stability of the compound in the ferromagnetic half-Heusler β-phase as expected from the elastic constants.