Phase stability and the effect of lattice distortions on electronic properties and half-metallic ferromagnetism of Co₂FeAl Heusler alloy: an ab initio study

Density functional theory calculations within the generalized gradient approximation are employed to study the ground state of Co₂FeAl. Various magnetic configurations are considered to find out its most stable phase. The ferromagnetic ground state of the Co₂FeAl is energetically observed with an optimized lattice constant of 5.70 Å. After that, the system was subjected under uniform and non-uniform strains, to see their effects on spin polarization (P) and half-metallicity. The effect of spin–orbit coupling is considered in the present study. Half-metallicity (and 100% P) is retained only under uniform strains started from 0 to +4%, and dropped rapidly from 90% to 16% for the negative strains started from −1% to −6%. We find that the present system is much sensitive under tetragonal distortions as half-metallicity (and 100% P) is preserved only for the cubic case. The main reason for the loss of half-metallicity is due to the shift of the bands with respect to the Fermi level (E _F). We also discuss the influence of these results on spintronics devices. (paper)