Prediction of half-metallic properties for the Heusler alloys Mn₂CrZ (Z=Al, Ga, Si, Ge, Sb): A first-principles study

First-principles FLAPW calculations were performed on the Mn₂CrZ (Z=Al, Ga, Si, Ge and Sb) alloys. Based on these results we predict two half-metallic ferromagnets (HMFs) namely Mn₂CrAl and Mn₂CrSb, and also find an energy gap in Mn₂CrGa which lies near the Fermi level. The energy gap lies in the majority spin band for Mn₂CrAl and Mn₂CrGa, whereas in the minority one for Mn₂CrSb. The calculated total spin magnetic moments M_t^cal are -1μ_B per unit cell for Mn₂CrAl and Mn₂CrGa, +1μ_B per unit cell for Mn₂CrSb and zero for Mn₂CrSi and Mn₂CrGe, which agree with the Slater-Pauling rule. The calculation indicates a large and localized magnetic moment of Cr at B site. This is meaningful for searching for new half-metallic antiferromagnets in Heusler alloys. The magnetic moment of Cr is found to increase with increasing atomic number of Z and is antiparallel to that of Mn. The change of Mn and Cr spin moments compensates each other and keeps the total spin moment as an integer when the Z atom is changed.