Ab initio study on stability of half-metallic Co-based full-Heusler alloys

We perform the first-principles density functional calculations of Co-based full-Heusler alloys, exploring 25 possible combinations of Co2 YZ (Y=Ti, V, Cr, Mn, and Fe; Z=Al, Ga, Si, Ge, and Sn) in order to clarify the stability for the Co-related atomic disorder, because this type of disorder is considered to degrade the spin polarization of Co2 YZ. We found that the disorder between Co and Y atoms correlates with the total valence electron charges around Y atom, because a difference in valence electron charges between Co and Y atoms leads to a different shape of the local potential at each site. This means that Ti-based alloys are better than Cr-, Mn-, and Fe-based alloys in preventing the atomic disorder between Co and Y atoms. From our results, we propose stable Co-based full-Heusler alloys with excellent prospects for half-metallic ferromagnets.