he Structural and Magnetic Properties of Ni2Mn1−xMxGa (M = Co, Cu)

This study investigates the structural and magnetic properties of Ni2Mn1−xMxGa (M = Co, Cu) to understand the influence of partial substitution of Mn sites with Co and Cu on these properties. Utilizing X-ray diffraction (XRD) and magnetization measurements, we reveal a first-order martensitic structural transition in Ni2MnGa from the cubic austenitic phase to a low-temperature complex tetragonal structure occurring at a temperature TM of 202 K. Additionally, we observe that the ferromagnetic order in the austenitic phase sets in at a critical temperature TC of 376 K. The results indicate that the Co-doped system maintains a highly ordered Heusler alloy L21 type structure for a concentration range of 0.05 ≤ x ≤ 0.12, while the Cu-doped compounds exhibit an L21 structure for 0.05 ≤ x ≤ 0.10. Notably, the ferromagnetic ordering temperature increases with higher concentrations of Co, while it declines with rising Cu concentrations. Both doping systems show an increase in TM with increasing concentrations of Co and Cu. Phase diagrams delineating these relationships have been constructed and contribute to a broader understanding of 3 d-electron concentration variations in the studied systems.