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MA: Fachverband Magnetismus
MA 24: Magnetic Materials I
MA 24.2: Vortrag
Mittwoch, 18. März 2015, 09:45–10:00, H 0112
Pressure and temperature dependent powder diffraction studies on magnetocaloric compounds of the series Mn5-xFexSi3 — •Paul Hering1, Karen Friese1, Thomas Brückel1, Anatoliy Senyshin2, Michael Hanfland3, Andrzej Grzechnik4, Mohammad Maswada1, and Ye Cheng1 — 1JCNS-2/PGI4, Forschungszentrum Jülich GmbH — 2MLZ, TUM, Garching — 3Inst. of Crystallo., RWTH Aachen — 4ESRF, Grenoble, France
Magnetic refrigeration based on the magnetocaloric effect hold a potential to replace conventional vapor compression cooling. Compared to other magnetocaloric materials, the compounds in the system Mn5-xFexSi3 have the advantage that they do not contain expensive rare earth elements like Gd, nor toxic elements like As. The compounds undergo a variety of magnetic phase transitions at different temperatures depending on the iron content [Songlin, et al., J. Alloys Comp. 334, 249-252 (2002)]. Therefore, this system is an ideal choice to gain a better understanding of the underlying mechanism of the MCE in multiple site driven magnetocaloric materials. We performed neutron and x-ray powder diffraction experiments as a function of temperature and could trace several magnetic and structural transitions through anomalies in the lattice parameter showing a close connection between lattice and spin degrees of freedom. Recent synchrotron powder experiments varying pressure and temperature simultaneously were performed to elucidate, -first- whether the influence of hydrostatic and `chemical pressure` (i.e. through the variation of composition) is equivalent, and -second- to follow the magnetic and associated structural transitions.