Effect of Co addition on the martensitic transformation and magnetocaloric effect of Ni-Mn-Al ferromagnetic shape memory alloys

摘要

A series of Ni_(50-x)Co_xMn_(32)Al_(18) (x = 3, 4, 5, 6, 7, and 8) alloys were prepared by the arc melting method. The martensitic transformation (MT) shifts to a lower temperature with increasing Co concentration and can be tuned to occur from a ferromagnetic austenite to a weak-magnetic martensite in the range of 6 ≤ x ≤ 8. The field-induced metamagnetic behavior was realized in Ni_(42)Co_8Mn_(32)Al_(18) sample in which a large magnetic entropy change of 7.7 J/kg K and an effective refrigerant capacity value of 112 J/kg were obtained under the field of 60 kOe. The large magnetocaloric effect and adjustable MT temperature suggest that Ni-Co—Mn-Al alloys should have promising potential as magnetic refrigerants.