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

The origin of the Slater–Pauling curve Mt=Zt−28 (Here Mt is the total spin moment and Zt is the number of valence electrons) in half-metallic Heusler alloys Mn2CuZ (Z=Ge and Sb) has been studied in detail. In Mn2CuZ the half-metallic gap has a similar origin like half-Heusler alloys. The Cu atom acts as an electron “donator” in Mn2CuZ, which contributes five d-electrons to the minority spin band of Mn2CuZ. So there are 14 valence electrons in the minority band of Mn2CuZ below the Fermi level. This is the origin of the S–P curve Mt=Zt–28. Finally, it is found that, by partial doping of Cu to the vacant site of half-metallic half-Heusler alloys, the magnetic moments of these can be tuned without destroying the half-metallicity. This can be a possible way to design new half-metals. ► 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.