Enhanced magnetic refrigeration properties in Mn-rich Ni-Mn-Sn ribbons by optimal annealing

Abstract

The influence of annealing time on temperature range of martensitic phase transition (ΔT A-M), thermal hysteresis (ΔT hys), magnetic hysteresis loss (ΔM hys), magnetic entropy change (ΔS M) and relative refrigeration capacity (RC) of the Mn-rich Ni 43 Mn 46 Sn 11 melt spun ribbons have been systematically studied. By optimal annealing, an extremely large ΔS M of 43.2J.kg -1 K -1 and a maximum RC of 221.0J.kg -1 could be obtained respectively in a field change of 5T. Both ΔT A-M and ΔT hys decreases after annealing, while ΔM hys and ΔS M first dramatically increase to a maximum then degenerates as increase of annealing time. A large effective cooling capacity (RC eff) of 115.4J.kg -1 was achieved in 60min annealed ribbons, which increased 75% compared with that unannealed ribbons. The evolution of magnetic properties and magnetocaloric effect has been discussed and proved by atomic ordering degree, microstructure and composition analysis.