Origin of the Z−28 rule in Mn2Cu-based Heusler alloys: A comparing study

► The origin of the Slater-Pauling curve Mt=Zt−28 in Mn2CuZ has been explained. ► A possible way to explore new half-metallic Heusler alloys was reported. ► The electronic structure of binary half-Heusler alloys Mn2Ge and Mn2Sb has been discussed.