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Magnetocaloric Response Of Non-Stoichiometric Ni(sub2)MnGa Alloys and the Influence of Texture

Published

Author(s)

Michael V. McLeod, Anit Giri, Brigitte A. Paterson, Cindi L. Dennis, H L. Zhou, S C. Vogel, Yong Ho Sohn, Robert D. Shull, B S. Majumdar

Abstract

Currently, there is significant interest in magnetocaloric materials for solid state refrigeration. In this work, polycrystalline Heusler alloys belonging to the Ni(sub2+x)Mn(sub 1-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 thought by some to be 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, S(subM), in the as-annealed state. Furthermore, MCE increased by up to 84 % with a 2 T field change when the samples were thermally cycled through the martensite to austenite transformation temperature while simultaneously under a constant mechanical load. The highest S(SubM) measured for the x=0.16 alloy for a 2 T magnetic field change was -18 J/kg-K, which is comparable to some of the best MCE values reported in the literature. Texture measurements suggest that preferential orientation of martensite variants contributed to an enhanced MCE in the stress-assisted thermally cycled state.
Citation
Acta Materialia

Keywords

magnetocaloric, NiMnGa alloy, polycrystalline, preferred orientation, twinning

Citation

McLeod, M. , Giri, A. , Paterson, B. , Dennis, C. , Zhou, H. , Vogel, S. , , Y. , Shull, R. and Majumdar, B. (2015), Magnetocaloric Response Of Non-Stoichiometric Ni(sub2)MnGa Alloys and the Influence of Texture, Acta Materialia (Accessed September 27, 2021)
Created November 1, 2015, Updated February 19, 2017