Magnetocaloric response of non-stoichiometric Ni2MnGa alloys and the influence of crystallographic texture. (15th September 2015)

• Record Type: Journal Article
• Authors: McLeod, M.V.; Giri, A.K.; Paterson, B.A.; Dennis, C.L.; Zhou, L.; Vogel, S.C.; Gourdon, O.; Reiche, H.M.; Cho, K.C.; Sohn, Y.H.; Shull, R.D.; Majumdar, B.S.
• Is Part Of: Acta materialia. Volume 97(2015)
• Page Start: 245
• Page End: 256
• Publication Date: 2015-09-15
• Subjects: Magnetocaloric -- NiMnGa alloy -- Polycrystalline -- Preferred orientation -- Twinning; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2015.06.059
• Languages: English
• ISSNs: 1359-6454

Abstract

Graphical abstract: The picture portrays the influence of martensite texture on the magnetocaloric effect of alloy x = 0.16, which exhibited the best coincidence of structural and magnetic transformations. Abstract: Currently, there is significant interest in magnetocaloric materials for solid state refrigeration. In this work, polycrystalline Heusler alloys belonging to the Ni2+x Mn1−x Ga family, with x between 0.08 and 0.24, were evaluated for the purpose of finding composition(s) with an enhanced magnetocaloric effect (MCE) close to room temperature. Differential scanning calorimetry (DSC) was successfully used to screen alloy composition for simultaneous magnetic and structural phase transformations; this coupling needed for a giant MCE. The alloy with x = 0.16 showed an excellent match of transformation temperatures and exhibited the highest magnetic entropy change, Δ SM, in the as-annealed state. Furthermore, the MCE increased by up to 84% with a 2 Tesla (T) field change when the samples were thermally cycled through the martensite to austenite transformation temperature while held under a constant mechanical load. The highest Δ SM measured for our x = 0.16 alloy for a 2 T magnetic field change was −18 J/kg K. Texture measurements suggest that preferential orientation of martensite variants contributed to the enhanced MCE in the stress-assisted thermally cycled state.