Search for half-metallic magnets with large half-metallic gaps in the quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z= Al, Ga, Si, Ge, As, Sb)

We investigate the electronic structure and magnetic properties of the twelve quaternary Hoosier alloys CoFeTiZ and CoFeVZ (Z=AI, Ga, Si, Ge, As, Sb) by using the first-principles calculations. It is shown that only CoFeTiSi, CoFeTiAs and CoFeVSb are half-metallic ferromagnets with considerable half-metallic gaps of 0.31, 0.18 and 0.17 eV, respectively. CoFeTiAl and CoFeTiGa are conventional semiconductors, and other alloys exhibit nearly hall-metallicity or their half-metallic gaps are almost zero eV. We also find that the hall-metallicities of CoFeTiSi, CoFeTiAs and CoFeVSb can be preserved under appropriate uniform and in-plane strains. The considerable half-metallic gaps and the robust hall-metallicities under uniform and in-plane strains make CoFeTiSi, CoFeTiAs and CoFeVSb promising candidates for spintronic applications. (C) 2014 Elsevier B.V. All rights reserved