Influence of Partial Substitution of Sn by Si on the Electrical, Mechanical, and Magnetic Properties of Ni₄₄Mn₄₄Sn₁₂ Heusler Alloys

The effect of substituting Sn with a fourth element on the functional properties of Heusler NiMnSn alloys has been reported in the literature. In the present work, the influence of the addition of Si to the Heusler NiMnSn system was evaluated, where Ni₄₄Mn₄₄Sn₁₂ (at.%), Ni₄₄Mn₄₄Sn_10.5Si_1.5 (at.%) and Ni₄₄Mn₄₄Sn₉Si₃ (at.%) alloys were prepared in an induction furnace without a controlled atmosphere, and were later characterized by optical microscopy, Vickers microhardness, electrical resistivity, and vibrating sample magnetometry. The results revealed that the partial replacement of Sn by 3 at.% Si did not modify the dendritic microstructure and the phases present at room temperature; however, it increased the percentage of the martensite phase from 51% to 76%. This modification in the percentage of this phase is responsible for reducing the average Vickers microhardness values (from 469 HV to 459 HV), increasing the electrical resistivity (from 1.3 mΩ mm to 2.21 mΩ mm), and decreasing the saturation magnetization (from 23.67 emu/g to 19.34 emu/g), coercivity (from 5.56 Oe to 5.14 Oe), and remanent magnetization (from 0.21 emu/g to 0.18 emu/g). With this, our results bring to light a new alternative for doping the NiMnSn alloy as a way of modifying the structural and electrical properties, constituting interesting parameters for technological applications.