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      Large reversible magnetocaloric effect in antiferromagnetic Ho 2O 3 powders

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          Abstract

          Giant magnetocaloric materials are highly promising for technological applications in magnetic refrigeration. Although giant magnetocaloric effects were discovered in first-order magnetic transition materials, it is accompanied by some non-desirable drawbacks, such as important hysteretic phenomena, irreversibility of the effect, or poor mechanical stability, which limits their use in applications. Here, we report the discovery of a giant magnetocaloric effect in commercialized Ho 2O 3 oxide at low temperature (around 2 K) without hysteresis losses. Ho 2O 3 is found to exhibit a second-order antiferromagnetic transition with a Néel temperature of 2 K. At an applied magnetic field change of 5 T and below 3.5 K, the maximum value of magnetic entropy change \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(-\Delta {{\rm{S}}}_{M}^{max})$$\end{document} , the refrigerant capacity (RC) were found to be 31.9 J.K −1.kg −1 and 180 J.K −1, respectively.

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          Giant Magnetocaloric Effect inGd5(Si2Ge2)

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            Transition-metal-based magnetic refrigerants for room-temperature applications.

            Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) have recently been demonstrated as a promising alternative to conventional vapour-cycle refrigeration. In a material displaying the MCE, the alignment of randomly oriented magnetic moments by an external magnetic field results in heating. This heat can then be removed from the MCE material to the ambient atmosphere by heat transfer. If the magnetic field is subsequently turned off, the magnetic moments randomize again, which leads to cooling of the material below the ambient temperature. Here we report the discovery of a large magnetic entropy change in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 14.5 J K-1 kg-1 and 18 J K-1 kg-1 for field changes of 2 T and 5 T, respectively. The so-called giant-MCE material Gd5Ge2Si2 (ref. 2) displays similar entropy changes, but can only be used below room temperature. The refrigerant capacity of our material is also significantly greater than that of Gd (ref. 3). The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field.
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              Recent developments in magnetocaloric materials

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                Author and article information

                Contributors
                boutahar.fsac@gmail.com
                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group UK (London )
                2045-2322
                24 October 2017
                24 October 2017
                2017
                : 7
                Affiliations
                [1 ]LabSIPE, Ecole Nationale des Sciences Appliquées, Université Chouaib Doukkali d’El Jadida, El Jadida, Plateau 24002 Morocco
                [2 ]LPMMAT, Université Hassan II-Casablanca, Faculté des Sciences Ain Chock, BP 5366 Mâarif-Casablanca, Morocco
                [3 ]ISNI 0000 0001 2112 9282, GRID grid.4444.0, Institut Néel, CNRS, Université Grenoble Alpes, ; 25 rue des Martyrs, BP 166 38042 Grenoble cedex 9, France
                Article
                14279
                10.1038/s41598-017-14279-y
                5655667
                29066735
                © The Author(s) 2017

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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