Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 19: POSTER Ia
MA 19.14: Poster
Dienstag, 17. März 2015, 09:30–13:00, Poster A
Thermodynamics and magnetism at the first-order magnetostructural transition in Mn3GaC powder and single crystal samples — •Franziska Scheibel1, Tino Gottschall2, Mahdiyeh Ghorbani Zavareh3, Moritz Riebisch1, Öznur Çakir4, Michael Farle1, and Mehmet Acet1 — 1Faculty of Physics and CENIDE Universität Duisburg-Essen, Duisburg, Germany — 2Material Science Technische Universität Darmstadt, Darmstadt, Germany — 3High Magnetic Field Laboratory HZDR, Dresden-Rossendorf, Germany — 4Physics Department Yildiz Technical University, Istanbul, Turkey
For magnetic refrigeration materials with a large adiabatic temperature-changes ΔT and large entropy changes ΔS are required. Such large changes are possible at first-order magnetostructural transitions (FOMST). At a FOMST, the thermal hysteresis limits the reversibility of ΔT. Therefore, materials with narrow thermal hysteresis play a major role in applications. Mn3GaC powder shows a FOMST from a ferromagnetic (FM) to an antiferromagnetic (AF) phase at 155 K with ΔS=15 Jkg−1K−1 and ΔT=4.8 K in 2 T field. Direct ΔT measurements show a high degree of reversibility at the transition. ΔT measurements for magnetic field rates of 1.1·10−2 Ts−1, 0.7 Ts−1 and 7.8·102 Ts−1 were done to understand the time-dependent properties of the transition process and the effect of hysteresis. The magnetocrystalline anisotropy energy for this material was determined from ferromagnetic resonance measurements on a Mn3GaC single crystal around the FOMST.
Work supported by the Deutsche Forschungsgemeinschaft (SPP 1599).