Magnetic-Field-Induced Isothermal Entropy Change Across the Magnetostructural Transition in Ni-Mn-Ga Melt-Spun Ribbons

• Published in: IEEE transactions on magnetics 2015-11, Vol.51 (11), p.1-4
• Main Authors: Zongbin Li, Sanchez-Valdes, C. F., Sanchez Llamazares, J. L., Yudong Zhang, Esling, Claude, Xiang Zhao, Liang Zuo
• Format: Article
• Language: English
• Subjects: Alloys; Annealing; Entropy; Joining; Magnetic fields; Magnetic separation; Magnetic transitions; Magnetism; Magnetocaloric effect; Magnetostructural transformation; Martensitic transformations; Melt spinning; Melt-spun ribbons; Metals; Ni-Mn-Ga alloys; Perpendicular magnetic anisotropy; Ribbons; Transformations
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2015.2438023

The phase transformation and the magnetocaloric effect of Ni 53 Mn 22 Ga 25 and Ni 52 Mn 26 Ga 22 ribbons were studied. It is shown that in melt-spun Ni 53 Mn 22 Ga 25 ribbons the magnetic transition and the martensitic transformation are well separated. For this sample, the austenite grains are columnar in shape with a typical preferential orientation of {001}A//ribbon plane. For a magnetic field change of 5 T, the maximum entropy change ΔS T max of -4.7 Jkg -1 K -1 is achieved at the vicinity of the martensitic transformation. For the Ni 52 Mn 26 Ga 22 ribbons, the structural transformation and the magnetic transition occurred simultaneously in both melt-spun and annealed ribbons. Owing to the coupled magnetostructural transformation, a ΔS T max of -11.4 Jkg -1 K -1 is reached for a magnetic field change of 5 T in melt-spun Ni 52 Mn 26 Ga 22 ribbons. After thermal annealing, ΔS T max increases to -30.0 Jkg -1 K -1 , which is almost three times higher as that of the initial melt-spun ribbons, due to the improved atomic ordering and the coupling of the intermartensitic transformation with the magnetostructural transformation.