Phase Transitions, Magnetocaloric Effect and Magnetoresistance in Ni–Co–Mn–Sn Ferromagnetic Shape Memory Alloy

The phase transitions, magnetocaloric effect and magnetoresistance in Ni₄₃Mn_46-xCo_xSn₁₁ (x=0–5) ferromagnetic shape memory alloys were investigated. With the increase of Co concentration, the temperatures of martensitic transformation and magnetic transition in austenitic phase increase rapidly, while the magnetic transition temperature in martensitic phase shows a small decrease. In Ni₄₃Mn₄₁Co₅Sn₁₁, a giant magnetic entropy change of 19.1 J/(kg·K) in the magnetic field of 10 kOe at 294 K, as well as a large magnetoresistance of -59% for the field change of 50 kOe at 281 K, is observed. These interesting phenomena are associated with the sudden changes of magnetization and resistance near the martensitic transition temperature. These results make the low-cost Ni–Mn–Co–Sn have promising application in magnetic refrigeration and magnetic sensor.