Enhanced Magnetocaloric and Mechanical Properties of Novel Mn-Ni-Cu and Mn-Ni-Ga Alloys for Near-Room Temperature Applications

Solid-state cooling relies on the caloric properties of materials like magnetocaloric, elastocaloric, and barocaloric, which respond to external applied fields such as magnetic fields, mechanical stress, and pressure. These caloric effects are crucial for improving energy efficiency and promoting sustainable practices. Ni-Mn-X (X = Ga, In, Sn, Sb)-based Heusler alloys have garnered significant attention due to their giant magnetocaloric effects. However, despite their potential, practical application of Heusler alloys is hindered by poor mechanical properties of Heusler alloys. In this study, two promising compositions within the Mn-Ni-Cu and Mn-Ni-Ga ternary alloys are selected based on thermodynamic calculations. These alloys exhibited notable magnetocaloric effects near room temperature with minimal thermal hysteresis. The optimal entropy change calculated at applied magnetic field of 1 Tesla, is found to be 4.48 J kg-1 K-1, reported for the first time in the Mn-Ni-Cu ternary alloy. In addition, mechanical behavior of investigated alloys is studied extensively. This approach aims to suppress the p-d orbital hybridization, which is associated with poor mechanical properties, by replacing Ga with Cu. First-principle calculations are also performed to validate the experimental findings of the structural, magnetic properties, and mechanical behavior of the investigated Mn-Ni-Cu and Mn-Ni-Ga alloys.