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MA: Fachverband Magnetismus
MA 52: Poster II
MA 52.68: Poster
Thursday, March 15, 2018, 15:00–18:00, Poster C
Structural investigations on Erythrosiderite-type compounds — •Tobias Fröhlich1, Ladislav Bohatý2, Betra Becker2, Arsen Gukasov3, Martin Meven4, and Markus Braden1 — 1II. Physikalisches Institut, Universität zu Köln — 2Institut für Kristallographie, Universität zu Köln — 3Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay — 4Heinz-Maier-Leibnitz Zentrum, Technische Universität München
Erythrosiderite-type compounds of the form A2[FeCl5(H2O)] were discovered as being magneto-electric. We investigate the crystal and magnetic structures of the compounds (NH4)2[FeCl5(H2O)] and Cs2[FeCl5(H2O)] . In contrast to the other erythrosiderite-type compounds, (NH4)2[FeCl5(H2O)] is multiferroic. We studied a structural phase transition occurring in this material well above the onset of magnetic order by single-crystal neutron diffraction. The structural transition can be attributed to the ordering of the NH4 groups. The compound Cs2[FeCl5(H2O)] plays an exceptional role in this material family: It differs from the other erythrosiderite-type compounds with respect to its crystal structure. While most erythrosiderite-type compounds crystallize in space group Pnma , this compound exhibits space group Cmcm associated with a different arrangement of the FeCl5O octahedra. Again, there is a structural phase transition occuring well above the magnetic ordering that was neglected for most investigations so far. We investigated both compounds by neutron and X-ray diffraction and present an analysis of their low-temperature crystal structures and its consequences for the magneto-electric properties.