Phase Stability of Ni–(Co)–Mn–<i>Z</i> (<i>Z</i> = Ga, In, Sb, Sn) Heusler Alloys

Abstract

Abstract—This work is devoted to the first-principle studies of phase stability and segregation stability of austenitic and martensitic phases of Heusler alloys Ni2 – xCoxMn1 + yZ1 – y (x = 0, 0.25, 0.5 and y = 0, 0.25, 0.5, 0.75; Z = Ga, In, Sb, Sn) with different types of magnetic ordering. Among all the considered compounds, only alloys Ni1.5Co0.5MnGa and Ni2MnGa in cubic and tetragonal structures with ferromagnetic ordering, respectively, as well as Ni2Mn2 in tetragonal structure with staggered and layer-by-layer antiferromagnetic ordering demonstrate stability. For these compositions, the presence of zero convex hull energy and the absence of reactions with positive decomposition energy are shown. The remaining compounds appear to be metastable both due to the presence of stable reactions with negative decomposition energy and decay reactions with positive decomposition energy. The number of decay reactions increases with increasing chemical disorder, i.e., deviation from stoichiometry.