Experimental investigation of martensitic transformation in Ni₂MnGa alloys with elemental substitutions

This research investigates the structural and magnetic properties of Ni (Co)-Mn-Sn alloys, focusing on their Curie temperature (T_C), martensitic transformation temperature (T_m), and change in total magnetization (Δμ_tot) as functions of the electron-to-atom ratio (e/a). Various alloy compositions, including Ni-Mn-Sn, Ni(Co)-Mn-Sn, Ni-Mn(Cr)-Sn, Ni(Co)-Mn(Cr)-Sn, Ni-Mn(C)-Sn, Ni(Co)-Mn(C)-Sn, and Ni(Co)-Mn-Sn(Al), were synthesized using high-purity arc-melting techniques under an argon atmosphere. The ingots were annealed to achieve homogeneity, followed by quenching to retain the desired phase structure. X-ray Diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDS) were employed for phase purity and composition verification. Magnetic properties were measured using Vibrating Sample Magnetometry (VSM) to determine T_C and Δμ_tot. Differential Scanning Calorimetry (DSC) was used to measure the martensitic transformation temperatures (T_m). The data revealed significant variations in T_C, T_m, and Δμ_tot with respect to the e/a ratio across different alloy compositions. Ni-Mn-Sn alloys exhibited the highest T_C (~420 K) and significant changes in magnetization (Δμ_tot ≈ 6μ_B per formula unit), indicating strong ferromagnetic ordering. The study provides valuable insights into the effects of elemental substitutions on the structural and magnetic properties of Ni(Co)-Mn-Sn alloys. These findings contribute to the development of advanced materials with tailored magnetic and structural properties, suitable for applications in magnetic refrigeration, sensors, and other magnetic devices. Future work will focus on optimizing these properties and exploring additional substitutions to further enhance the desired characteristics.