Negative and positive magnetocaloric effect in Ni–Fe–Mn–Ga alloy

• Published in: Journal of magnetism and magnetic materials Vol. 309; no. 1; pp. 96 - 99
• Main Authors: Duan, Jingfang, Huang, Peng, Zhang, Hu, Long, Yi, Wu, Guangheng, Rongchang Ye, Chang, Yongqin, Farong Wan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2007; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Curie temperature [formula omitted]; Exact sciences and technology; Magnetic entropy change; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Magnetocaloric effect, magnetic cooling; Martensitic transformations; Martensitic transition temperature [formula omitted]; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; 75.50.Cc; Magnetic entropy change; 75.80.+q; Martensitic transition temperature T M; Curie temperature T C; 75.30.−m; Nickel alloys; Curie point; Magnetization; Martensitic transition temperature TM; Curie temperature TC; Magnetic entropy change; Martensitic transformations; Magnetic field effects; Iron alloys; Gallium alloys; Magnetic transitions; Magnetocaloric effects; Manganese alloys; 75.80.+q; 75.30.-m; 75.50.Cc; Transition element alloys
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2006.06.017

The phase transition process and magnetic entropy change Δ S of Ni 54.5 FeMn 20 Ga 24.5 alloy were studied. Substitution of Fe for Ni increases the Curie temperature and decreases the temperature of martensitic phase transition. The transition from ferromagnetic martensitic to ferrormagnetic austenitic state leads to an abrupt increase of magnetization below 0.5 T and an abrupt decrease of magnetization above 0.5 T. The sign of Δ S changes from positive to negative with increasing the applied field from 0.5 to 2 T. The maximal value of the positive magnetic entropy change Δ S is about 3.1 J/kg K for the applied field from 0 to 0.5 T. The increase of applied field from 1.5 T results in a negative Δ S . The peak of negative Δ S is - 2.1 J / kg K for a field change of 2 T.