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MA: Fachverband Magnetismus
MA 62: Magnetic Imaging (Experimental Techniques)
MA 62.3: Vortrag
Freitag, 24. März 2017, 10:00–10:15, HSZ 403
Investigating magnetism in nano-sized goethite particles — •David M. Bracher1,2, Tatiana M. Savchenko1, Marcus Wyss2, Giorgia Olivieri3, Matthew A. Brown3, Frithjof Nolting1, Martino Poggio2, and Armin Kleibert1 — 1Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland — 2Department of Physics and Astronomy, University of Basel, CH-4056 Basel, Klingelberstrasse 82, Switzerland — 3Laboratory for Surface Science and Technology, Department of Materials ETH Zürich, CH-8093,HCI G543
Goethite (α-FeOOH) is abundant in the earth crust and, thus, an important marker for paleomagnetism and paleoclimatology. Bulk goethite exhibits antiferromagnetic order at room temperature. However, nano-sized goethite often has of a complex polycrystalline morphology and possibly altered magnetic properties. Combining X-ray photo-emission electron microscopy with scanning electron microscopy we correlate the magnetism and morphology of individual goethite nanoparticles. Synthetic goethite nanoparticles are dispersed on silicon substrates with gold markers facilitating particle identification. X-ray magnetic linear dichroism is capable of probing antiferromagnetism, while X-ray magnetic circular dichroism tracks eventual uncompensated magnetic moments, which may emerge from structure and size of the particles. Angular- and temperature-dependent investigations suggest antiferromagnetism in the particles below the bulk Néel temperature and anisotropic properties at room temperature without indication of uncompensated moments. These results will be discussed with respect to the morphology of the particles.