Enhancing the half-metallicity of equiatomic quaternary Heusler compound CoFeCrGe via atomic doping

Recently, the equiatomic quaternary Heusler alloy CoFeCrGe has been demonstrated to be half-metallic ferromagnet and possesses high Curie temperature of 866 K (Enamullah et al., 2015). However, its Fermi level locates at the edge of conduction band, leading to an unstable half-metallicity, restricting its further application in spintronics devices. In the present work, in order to enhance the half-metallicity of CoFeCrGe, two kinds of atomic doping including mono-atomic and co-atomic doping are employed to improve the electronic structure. In addition, the magnetic properties of the compound at different doping concentrations are studied. The V mono-doping could be easily formed, while it further decreases the spin polarization. Although As mono-doping is benefit for the electronic structure of compound, it is difficult to be obtained owing to its positive formation energy. As for V + As co-doped compound CoFeCr1-xVxGe1-yAsy, Fermi level is adjusted to near the middle of the spin down energy gap when the co-doping concentration (x, y) reaches to (0.25, 0.5). Therefore, the co-doped compound CoFeCr0.75V0.25Ge0.5As0.5 possesses robust half-metallicity.