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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).