Slater–Pauling behavior and half-metallicity in Heusler alloys Mn2CuZ (Z = Ge and Sb)

The Slater–Pauling behavior and half-metallic properties of full-Heusler alloys Mn2CuZ (Z = Ge and Sb) have been studied by first-principles calculations. It is found that the total spin moment (Mt) and the number of valence electrons (Zt) follow a Slater–Pauling rule of Mt = Zt − 28 rather than Mt = Zt − 24 in normal Heusler alloys. Mn2CuSb is predicted to be a half-metal at equilibrium lattice constant and Mn2CuGe is also half-metallic with a small expansion of the lattice. Mn2CuGe and Mn2CuSb are both ferrimagnets with total spin moment of +0.97μB/f.u. and +2.00μB/f.u., respectively. Considering Mn2CuGe and Mn2CuSb have 29 and 30 valence electrons, the S-P curve of Mt = Zt − 28 works quite well. This different S-P rule is strongly related to the low-lying Cu states and the weak hybridization between the d states of Cu and Mn.

► A Slater-Pauling rule of Mt = Zt − 28 rather than Mt = Zt − 24 in normal half-metallic Heusler alloys has been reported.
► Different origin of the half-metallic gap in full-Heusler alloys is reported, the cause of this difference is discussed.
► Comparison with preceding studies on Mn2CuSb has been made, unusual results in the latter have been discussed.