Berlin 2018 – scientific programme
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MA: Fachverband Magnetismus
MA 7: Focus Session: Magnetism in Materials Science: Thermodynamics, Kinetics and Defects I (joint session MM/MA)
MA 7.7: Talk
Monday, March 12, 2018, 12:45–13:00, TC 010
Spin-lattice effects in LaFe11.6Si1.4 revealed by powder diffraction — •Tom Faske1, Wolfgang Donner1, and Markus Hölzel2 — 1TU Darmstadt, Materials Science, Structure Research, Darmstadt, Germany — 2Heinz Maier-Leibnitz Zentrum, Garching, Germany
LaFe13−xSix (x = 1.0 − 1.6) is a promising material class for application in magnetic cooling and has been extensively studied in recent years. For x ≤ 1.6 it exhibits a first order magneto-structural phase transition around 200 K which becomes second order for x > 1.6. The first-order transition is accompanied by a large isothermal entropy change |ΔSiso| in conjunction with a high adiabatic temperature change |ΔTad|, which are both important figures of merit for a potential magnetocaloric application.
Here we report on the detailed study of the first-order phase transition of LaFe13−xSix by means of temperature and magnetic field dependent x-ray and neutron powder diffraction. External magnetic fields increase the Curie temperature by ≈ 4 K/T, so that the phase transition could be induced thermally and by applying magnetic fields of up to 5 T during the diffraction experiments. In a narrow magnetic field and temperature range, both phases were present in the diffraction patterns. Subtle structural differences in the two-phase region between the magnetic field and temperature induced phase transitions revealed a change in the entropy transfer of the two systems.