Innovative Processing of Highly Efficient Rare Earth Free Magnetocaloric Materials

Report No. ARL-TR-6866
Authors: Anit Giri and Kyu Cho
Date/Pages: March 2014; 22 pages
Abstract: In order to fabricate a magnetic cooling system, it is necessary to develop rare earth free polycrystalline magnetocaloric materials (MCMs) with large magnetocaloric effect (MCE). To increase the MCE, we applied an innovative processing technique to manipulate crystallographic alignment in polycrystalline Ni2+xMn1-xGa rare-earth free alloys consisting of thermal cycling about the martensite phase transition temperature under a compressive stress. After crystallographic alignment, there was as high as 79% enhancement of the maximum magnetic entropy change for the magnetic field change of 7 T. Texture measurements using neutron diffraction have shown that thermal cycling leads to crystallographic alignment of the easy magnetization axis along the loading direction, which explains the MCE enhancement by up to 79%. Overall, a methodology for enhancing solid state magnetocaloric cooling has been established.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 2014