Dresden 2014 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 42: Magnetic Materials III
MA 42.9: Vortrag
Donnerstag, 3. April 2014, 17:15–17:30, HSZ 04
Study of the magnetocaloric effect in MnFe4Si3 — •Paul Hering1, Karen Friese1, Jörg Voigt1, Thomas Brückel1, Anatoliy Senyshyn2, Nadir Aliouane2,3, and Andrzej Grzechnik4 — 1JCNS-2/PGI 4, Forschungszentrum Jülich — 2MLZ, TUM, Garching — 3PSI, Villigen, Schweiz — 4Inst. of Crystallo., RWTH Aachen
Due to global warming, there is an increasing demand for more energy-efficient refrigeration technologies. Magnetocaloric devices are candidates to replace conventional vapor compression cooling, as they have potentially 20-30% lower energy consumption. MnFe4Si3 is a promising candidate for magnetic cooling at ambient temperatures [Songlin, et. al., J. Alloys Comp. 334, 249 (2002)]. To understand the interplay of the spin and lattice degrees of freedom in this material, we studied the magnetic properties and the temperature dependent evolution of its hexagonal structure. The compound undergoes a magnetic phase transition close to 300K, which is accompanied by a modestly high magnetocaloric effect (MCE) of 2.9 J/kg K at a magnetic field change from 0T to 2T. Refinements with the program Jana2006 using single crystal neutron and x-ray data simultaneously show that in the ferromagnetically ordered structure the magnetic moments are aligned in the a,b-plane. Magnetic susceptibility measurements confirm the easy axis of magnetization perpendicular to the c-axis. Lattice parameter obtained from neutron powder diffraction data show a discontinuous change at the temperature of the onset of magnetic ordering. This clearly indicates the first order character of the phase transition and explains the relatively high MCE.