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

摘要

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 Ni₄₃Mn₄₆Sn₁₁ melt spun ribbons have been systematically studied. By optimal annealing, an extremely large ΔS_M of 43.2?J.kg?1K?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.