Half-metallic Na-based half-Heusler alloys as potential spintronic materials.

In this study, we investigate the structural, electronic, magnetic and mechanical properties of the Na-based half-Heusler alloys XYZ composed of X=Na ( p 0 atom); Y=K, Rb, Cs ( d 0 atoms) and a main body sp atom Z=C, Si, Ge, Sn, Pb by using the DFT based full-potential WIEN2k package. We compare the total energy vs volume of ferromagnetic, antiferromagnetic and non-magnetic half-Heusler structures to obtain the stable magnetic structure. Calculations show that compounds are stable in the half-Heusler β -phase and the ferromagnetic state. From 15 alloys under study, 13 of them showed half-metallic behavior in the minimum-energy half-Heusler phase at the optimized lattice constant. We show that all compounds have the same total magnetic moment equal to 2 μ B . The band structure and the density of states of half-Heusler alloys are obtained. The elastic constants C 11 , C 12 and C 44 of the single crystal and the related elastic moduli G, B, E, υ of the polycrystalline aggregates are also calculated and used to study the mechanical stability of these alloys. Furthermore, the average, transverse, longitudinal sound velocities and the Debye temperature for these compounds are calculated. Finally, the Curie temperatures T C of the half-Heusler alloys are estimated by using the mean field approximation. The estimated Curie temperatures shows that these compounds preserve the ferromagnetic state and magnetic polarization at temperatures much higher than the room temperature and may be suitable for spintronic applications. [ABSTRACT FROM AUTHOR]