Magnetic properties and magnetic entropy change in Heusler alloys Ni 50 Mn 35 − x Cu x Sn 15

The influence of Cu substitution for Mn on magnetic properties and magnetic entropy change has been investigated in Heusler alloys, Ni50Mn35−xCuxSn15 (x = 2,5 and 10). With increasing Cu content from x = 2 to x = 5, the martensitic transition temperature, TM , decreases from 220 K to 120 K. Further increasing Cu up to x = 10 results in the disappearance of TM . For samples Ni50Mn33Cu2Sn15 and Ni50Mn30Cu5Sn15, both martensitic and austenitic states exhibit ferromagnetic characteristics, but the magnetization of martensitic phase is notably lower than that of austenitic phase. The magnetization difference, M , across the martensitic transition leads to a considerably large Zeeman energy, μ0 M · H , which drives a field-induced metamagnetic transition. Associated with the metamagnetic behavior, a large positive magnetic entropy change S takes place around TM . For the sample Ni50Mn33Cu2Sn15, S reaches 13.5 J/kg·K under a magnetic field change from 0 to 5 T. PACS 75.30.Sg · 75.20.En · 75.50.Cc