Magnetostructural transition and magnetocaloric effect in Ni-Mn-In-(Co) alloys

摘要

A study of the magnetostructural transition and magnetocaloric effect in Ni-Mn-In-(Co) bulk and ribbon samples was carried out. A significant shift of martensitic transition temperature by the application of the magnetic field occurs below room temperature in Ni_(50)Mn_(34)In_(16) bulk sample. The positive and negative magnetic entropy changes were obtained around structural and ferromagnetic transitions, respectively. To tune the martensitic transition close to room temperature, the application of pressure and the alloying of Co were performed. The martensitic transition temperature was increased by 35 K by applying a pressure of 9.6 kbar. In Ni_(45)Mn_(37)In_(13)Co_5 bulk sample, a magnetostructural transition with a small hysteresis of 8 K was observed around 325 K. In contrary, Ni_(45)Mn_(37)In_(13)Co_5 ribbon has a relatively large hysteresis of 18 K. The irreversible magnetostructural transition due to the large hysteresis leads to a variation in the magnetocaloric effect in dependence on sample pre-history.