Features of the Influence of Atomic Ordering on the Structural and Magnetic Properties of the Heusler Alloy Ni₂Mn_1.5Sn_0.5

The effect of atomic ordering on the structural and magnetic properties of the crystal structures of the austenite and martensite phases of the Heusler alloy Ni₂Mn_1.5Sn_0.5 has been studied within the density functional theory (DFT). The cubic L2₁, tetragonal L1₀, and orthorhombic 4O structures are considered. The L2₁ phase demonstrates a lower stability in view of its higher energy with respect to the L1₀ and 4O phases. The presence of the antiferromagnetic plane containing Mn atoms in the computational box of L1₀ makes it less favorable by 10 meV/atom in comparison with the 4O phase. However, dilution of the antiferromagnetic plane with Sn atoms leads to increasing stability of the L1₀ structure. An energetically favorable atomic configuration was predicted, at which the L1₀ structure becomes more favorable by 21 meV/atom than the 4O structure. The obtained results qualitatively describe the existing experimental data.