Dresden 2009 – wissenschaftliches Programm
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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 40.58: Poster
Freitag, 27. März 2009, 11:00–14:00, P1A
Anisotropy of antiferromagnetic 180∘ domains in magnetoelectric LiMPO4 — •Anne Zimmermann1, Bas B. van Aken1, Jean-Pierre Rivera2, Hans Schmid2, and Manfred Fiebig1 — 1HISKP, University of Bonn, Germany — 2Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Switzerland
The investigation of compounds forming 180∘ domains directly leads to the inherent magnetic effects determining the AFM domain topology. The group of lithium-orthophospates LiMPO4 (M = Co, Fe, Mn, Ni) is a good system for studying the parameters determining the formation of 180∘ domains, because of its variety of magnetically similar but pronouncedly anisotropic compounds. The crystallographic symmetry of LiMPO4 is mmm. As magnetic symmetry, mmm’ (M = Co, Fe) and mm’m (M = Mn, Ni) are obtained.
Here we report on the observation of AFM 180∘ bulk domains in LiMPO4 (M = Co, Fe, Ni) by optical second harmonic generation (SHG). SHG coupling linearly to the AFM order parameter was identified in spectroscopy measurements and used for imaging domains. In spite of their similar crystallographic and magnetic structure the three compounds display drastically different domain patterns. Possible explanations for this unexpected diversity are discussed. In addition, we observed domains of a magnetic vortex (so-called ferrotoroidic) state that coexist with the AFM domains in LiCoPO4. For LiNiPO4 we showed that a magnetic field is sufficient to orient the AFM 180∘ domains via the magnetoelectric effect. - Work supported by the SFB 608 of the DFG.