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 (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 43.2 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 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 115.4 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.