Improving Hard Magnetic and Magnetocaloric Properties of Nanocrystalline Intermetallics
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Improving Hard Magnetic and Magnetocaloric Properties of Nanocrystalline Intermetallics L. Bessais, R. Guetari, K. Zehani, J. Moscovici and N. Mliki MRS Advances / FirstView Article / May 2016, pp 1 - 6 DOI: 10.1557/adv.2016.243, Published online: 11 April 2016
Link to this article: http://journals.cambridge.org/abstract_S2059852116002437 How to cite this article: L. Bessais, R. Guetari, K. Zehani, J. Moscovici and N. Mliki Improving Hard Magnetic and Magnetocaloric Properties of Nanocrystalline Intermetallics. MRS Advances, Available on CJO 2016 doi:10.1557/adv.2016.243 Request Permissions : Click here
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MRS Advances © 2016 Materials Research Society DOI: 10.1557/adv.2016.243
Improving Hard Magnetic and Magnetocaloric Properties of Nanocrystalline Intermetallics.
L. Bessais1 , R. Guetari1 , K. Zehani1 , J. Moscovici1 and N. Mliki2 . 1 CMTR,
ICMPE, UMR7182, CNRS − UPEC, 2-8 rue Henri Dunant F-94320 Thiais, France,
2 LMOP,
Faculty of Science of Tunis, University of Tunis El Manar, Tunisia,
ABSTRACT Structural and magnetic properties of nanocrystalline P 6/mmm R(Fe,M)9 C are presented. Their structure is explained with a model based on the R1−s (Fe,M )5+2s formula (s = vacancy rate) where s R atoms are statistically substituted by s transition metal pairs. The maximum coercivity is obtained for low Ga/Si content for auto-coherent diffraction domain size 30 nm. This controlled microstructure might lead to hard permanent magnet materials. Furthermore, the influence of small amount of Dy substitution on magnetocaloric properties of R-Fe systme is reported. The potential for using these low-cost iron based nanostructured RFe9 powders in magnetic refrigeration at room temperature is also discussed.
INTRODUCTION The comprehension of the structure transformation from the nanocrystalline precursor to the equilibrium phases 2/17 is still open to discussion. Both precursors are relevant of the P 6/mmm space-group and generally known as TbCu7 , derived from CaCu5 [1] while equilibrium structure R¯3m constitute super-lattices of the hexagonal sub-cell. However, we have recently demonstrated by Rietveld analysis coupled to M¨ossbauer spectroscopy that the precursor of Sm2 Fe17 is SmFe9 [2,3]. In the last decade, there has been an increased interest in magnetocaloric materials. Among many of the applications, the current interest has been on magnetic refrigeration near room temperature because that was being energetically more favorable [4,5]. Most of the current prototypes for room temperature magnetic refrigeration have used rare-earth (R) based materials [5,6]. However, some Fe-rich R2 Fe17 compounds have shown a magnetocaloric properties comparable with those of Gd-based compounds. In addition, these alloys are of interest due to lower cost of the main component (Fe) and easy fabrication procedures [7-13].
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