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

Abstract

The influence of Cu substitution for Mn on mag- netic 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 , de- creases from 220 K to 120 K. Further increasing Cu up to x = 10 results in the disappearance of TM .F or 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 differ- ence, �M , across the martensitic transition leads to a con- siderably large Zeeman energy, μ0�M · H , which drives a field-induced metamagnetic transition. Associated with the metamagnetic behavior, a large positive magnetic en- tropy changeS takes place around TM . For the sample Ni50Mn33Cu2Sn15 ,� S reaches 13.5 J/kg·K under a mag- netic field change from 0 to 5 T.