Inverse magnetocaloric effect and magnetoresistance associated with martensitic transition for Cu-doped Ni-Mn-In Heusler alloy

In this study, we reported the influence of replacing Cu for Ni on the crystal structure, martensitic transformation, and magnetic properties for polycrystalline Ni50-xCuxMn37In13 (x=5 and 7) quaternary alloys. It was found that the studied alloys undergo a first-order martensitic transformation from ferromagnetic austenite to paramagnetic martensite near room temperature. With increasing Cu content, the martensitic transformation significantly shifts toward a lower temperature, and fully splits off from the Curie transition of austenite, which enhances the difference in magnetization between the two phases for the alloy with x=7. Moreover, both inverse magnetocaloric and magnetoresistance effects during reverse martensitic transformation were also studied in these two alloys. In comparison to Ni50-xCuxMn37In13 with x=5, an optimized refrigerant capacity (approximate to 100Jkg(-1)) and a considerable magnetoresistance (47%) were obtained in Ni43Cu7Mn37In13 alloy for the magnetic field change of 30kOe. In addition, the magnetic measurements with hydrostatic pressure demonstrate that the magnetoresistance in this system mainly arises due to the electron-lattice scattering triggered by structural transition.