Improvement of the Half-Metallic Stability of Co2FeAl Heusler Alloys by GeTe-Doping

The electronic and magnetic properties of the typical Heusler compound Co₂FeAl with GeTe doping were investigated by means of first principles calculations within local spin-density approximation +U. The calculations indicate that both Co₂FeAl and GeTe-doped Co₂FeAl are half-magnetic ferromagnets. The Fermi energy (E_F) of GeTe-doped Co₂FeAl is located in the middle of the gap of the minority states instead of around the top of the valence band as in Co₂FeAl. Moreover, the bandgap of GeTe-doped Co₂FeAl (1.01 eV) is much wider than that of Co₂FeAl (0.74 eV). These improved electronic structures will make GeTe-doped Co₂FeAl more stable against temperature variation. As for the magnetic properties, it was found that the substitution of GeTe for Al results in an increase in magnetic moment. The calculation results show that after doped with GeTe, the Fe-Fe distance in the Co₂FeAl cell becomes larger, which results in a stronger exchange interaction and consequently a larger magnetization density, leading to the increase in magnetic moment. Therefore, the expected excellent stability, wider bandgap, and larger magnetic moment of the GeTe-doped Co₂FeAl make it more suitable for spintronic applications than Co₂FeAl.