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

The influence of annealing time on temperature range of martensitic phase transition (Delta TA-M), thermal hysteresis (Delta T-hys), magnetic hysteresis loss (Delta M-hys), magnetic entropy change (Delta S-M) and relative refrigeration capacity (RC) of the Mn-rich Ni43Mn46Sn11 melt spun ribbons have been systematically studied. By optimal annealing, an extremely large Delta S-M of 43.2 J. kg(-1)K(-1) and a maximum RC of 221.0 J. kg(-1) could be obtained respectively in a field change of 5 T. Both Delta TA-M and Delta T-hys decreases after annealing, while Delta M-hys and Delta S-M first dramatically increase to a maximum then degenerates as increase of annealing time. A large effective cooling capacity (RCeff) of 115.4 J. kg(-1) was achieved in 60 min 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