Berlin 2015 – scientific programme
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MA: Fachverband Magnetismus
MA 32: Spin Structures and Magnetic Phase Transitions
MA 32.6: Talk
Wednesday, March 18, 2015, 16:30–16:45, EB 202
Reversible processes in minor loop hysteresis at the first-order magnetostructural transition in NiMnX (X=In, Sn) — •Franziska Scheibel1, Tino Gottschall2, Michael Farle1, and Mehmet Acet1 — 1Faculty of Physics and CENIDE Universität Duisburg-Essen, Duisburg, Germany — 2Material Science Technische Universität Darmstadt, Darmstadt, Germany
One key factor for efficient magnetic refrigeration is the reversibility of the adiabatic temperature-change ΔT when the external magnetic field is reversed. Even if ΔT is large in the range of a first-order magnetostructural transition (FOMST), the thermal hysteresis of the transition can limit its reversibility [1-2]. Materials with sufficiently narrow thermal hysteresis shows a reversible ΔT in a minor loop of the transition. NiMnX (X=Sn, In) Heusler alloys show a FOMST from a low temperature martensite state with low magnetization to a high temperature austenite state with a higher magnetization. The transition temperatures are around room temperature and the hysteresis is smaller than 10 K. To understand the reversible processes in the minor loops adiabatic ΔT and magnetostriction been measured simultaneously in an externally applied field up to 5 T. The magnetostriction behavior of the material is directly related to the volume ratio of matrensite- to austenite phase.
Work supported by the Deutsche Forschungsgemeinschaft (SPP 1599).
I. Titov et al., J. Appl. Phys. 112, 073914 (2012)
J. Liu et al., Nature Materials 11, 620-626 (2012)