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MA: Fachverband Magnetismus
MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)
MA 40.61: Poster
Freitag, 27. März 2009, 11:00–14:00, P1A
Magnetic structure in multiferroic pyroxenes: (Na, Li)FeSi2O6 — •Max Baum1, Alexander C. Komarek1, Navid Qureshi1, Petra Becker2, Ladislav Bohatý2, Martin Meven3, M. Teresa Fernandez Diaz4, Paul Steffens4, and Markus Braden1 — 1II. Phys. Inst., Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — 2Inst. für Geologie und Mineralogie, Universität zu Köln, Zülpicher Str. 49b, 50674 Köln, Germany — 3Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Lichtenbergstr. 1, 85747 Garching, Germany — 4Institut Laue-Langevin, BP 156, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France
(Na,Li)FeSi2O6 exhibit multiferroic properties. Previous neutron diffraction experiments on powder samples of both compounds were interpreted in a commensurate model with antiferromagnetically coupled FeO6 chains of anti- or ferromagnetic character. Our triple-axis result of a single crystal is at odds with the former published commensurate model for magnetic ordering: magnetic ordering is incommensurate in NaFeSi2O6 with a temperature independent modulation. Magnetic satellites appear at q-positions corresponding to an incommensurate modulation vector (0,0.23,0). Based on powder neutron diffraction data, Redhammer et al. propose the Shubnikov group P21/c as the magnetic space group for LiFeSi2O6. This corresponds in antiferromagnetic ordering within and between the FeO6 chains. Our measurement on a single crystal reveals the Shubnikov group P21/c' which is equivalent to ferromagnetic coupling within the chains and antiferromagnetic coupling between the chains.