Magnetic properties and magnetic entropy change in Heusler alloys Ni50Mn35−x Cu x Sn15

The influence of Cu substitution for Mn on magnetic properties and magnetic entropy change has been investigated in Heusler alloys, Ni50Mn35−x Cu x Sn15 (x=2,5 and 10). With increasing Cu content from x=2 to x=5, the martensitic transition temperature, T M , decreases from 220 K to 120 K. Further increasing Cu up to x=10 results in the disappearance of T M . 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, ΔM, across the martensitic transition leads to a considerably large Zeeman energy, μ 0ΔM⋅H, which drives a field-induced metamagnetic transition. Associated with the metamagnetic behavior, a large positive magnetic entropy change ΔS takes place around T M . For the sample Ni50Mn33Cu2Sn15,ΔS reaches 13.5 J/kg⋅K under a magnetic field change from 0 to 5 T.