Enhanced magnetic entropy change and working temperature interval in Ni-Mn-In-Co alloys

High magnetic entropy change and wide working temperature interval are both of great importance for the application of magnetic refrigerant working materials. Here Ni-Mn-In-Co alloys with oligocrystalline structure were produced by annealing heat treatment and the giant magnetocaloric effect and large working temperature interval were confirmed. The annealing increases the magnetization difference ΔM between martensite and austenite. The annealed alloy subjects to a reverse martensite to austenite and an intermediate phase transformation upon heating. The two-stage field-induced reverse transformation, contribute to a maximum magnetic entropy change of 37.1 J/kgK at 309 K under a magnetic field of 50000 Oe, were observed for the first time. In addition, a broadened working temperature interval of ∼22 K was obtained owing to the intermediate phase transformation. The giant room-temperature MCE in quaternary Ni-Mn-In-Co alloys is promising for magnetic refrigeration.