By Prof. Daniel Fruchart, Institut Néel, CNRS, Grenoble France.
The structural and magnetic properties of the MgCu2-type of R(Fe0.25Co0.75)2 compounds with R = Ho and Er and their hydrides R(Fe0.25Co0.75)2H~3 were investigated. Magnetization measurements versus temperature in a weak magnetic field indicate that all materials are ferrimagnets with Curie temperature TC = 455 and 445 K, 124 and 75 K for the Ho and Er compounds and for their hydrides, respectively. At 5 K, magnetization measurements vs field reveal rather close value, e.g. under 7 T: ~120 Am2/kg for the Ho systems and ~ 100 Am2/kg for the Er systems. The itinerant type of the RCo2 magnetism operating at very low temperature can be superseded by a localized picture e.g. when some Fe is substituted to Co, leading to stronger exchange interactions for ordering temperatures higher than RT. Conversely, hydrogen insertion leads to reduce the forces of the magnetic interactions (mainly for Co) thus permitting to monitor with x the ordering temperature at a rather constant magnetization level.
The magnetic entropy change (−∆SM) and the refrigerant capacity (RC) of R(Fe0.25Co0.75)2H~3 systems were analyzed from isothermal magnetization experiments under field changes between 0 and 7 T. These measurements reveal interestingly rather high magnetocaloric contributions down to 150 K, then larger for the hydrides than for the starting compounds. This suggests potential interests for low temperature operations, and furthermore for specific cooling applications from RT using dedicated mixtures of R(Fe0.25Co0.75)2 and R(Fe0.25Co0.75)2H~3.
Co-authors
I. Chaaba1, S. Othmani1, S. Haj-Khlifa2, P. de Rango2, D. Fruchart2
(1) Laboratoire des Technologies des Systèmes Smart, Sfax, Tunisia.
(2) Institut Néel & Université Grenoble Alpes, France.
Biography
Daniel FRUCHART, Emeritus CNRS Director, Institut Néel, Grenoble, France. Masters Fund. Maths, Phys. & Crystal., Hab Th. (76).
Research group Intermetallics & Interstitials – Energy Conversion, Institut Néel (82-09).
Co-Found McPhy Energy – Hydrides & Tanks. Found HollyFlow – Materials & Systems for Energy.
Associate Professor, OSU – USA (83)
Head French-Spanish European Lab. MANES (94-02).
European School Committee HERCULES (94-09).
Responsible for > 32 R&D industry, institution and international contracts + 9 EU contracts (CEAM I & II, Nitromag, HYSTORY, NessHy, NanoHy, InsidesPores, StorHy, ATLAS), PICS FRBR (Russia), LIA Xi’an (China)
Supervision > 41 PhD.
Published > 844 papers, mostly in peer reviewed journals. Contribute > 20 books. 14 Patents-CNRS & Industry: RE-Magnets, Na-Elimination from Surgenerator, Arc-melter, Magnetic Nano-arrays, Metal hydrides, Metal hydride tanks, SPD metallurgy. Magnetocalorics
Interests: Magnetic materials: Structure determination, Fund. & appl. magnetic materials (hard, soft, magnetocaloric). Metal-Hydrogen systems: Fund. – structure, physics & appl. properties (storage, HD & HDDR-processes), Tanks. Metallurgy: Severe Plastic Deformation, In up to 7 GPa H2, In magnetic fields (> 10 T). Thin deposits: MOCVD, PAVD. Neutron scatter. & X-ray spectro.: Powder/crystals, magnetism, QNS, SANS, EXAFS, XANES, XMCD
HIRSCH FACTOR 45 – RESEARCH GATE > 71 – PUBLICATIONS > 850 – CITATION INDEX > 9700
Awards 1-French Div. Mineral Chem. & Metall., 2-Soc. Mater. Spain 3-Bétancourt-Perronet, 4-ADEME Magnetocaloric, 5-French Phys. Soc. – Hydrogen Storage.
Committees:
Chair Solid StatePhysics, LURE French Synchrotron, 99-03. Magnetic Structure, Inst. Laue-Langevin, 00-02. French Neutron Scattering Division, 98-00. French Neutron Society, 98-01. IAE Expert & IAEA Observer.
Intern. Steering Committees of 5 Conferences – Organised 8 Int. Conferences
Edit. Board of IJHE (98-12) + Ed. Special Issue (15). Scientific Board of MDPI publishers (18)
Complete refs can be found at: www.researchgate.net/profile/D_Fruchart