Berlin 2015 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Focus: Towards quantitative magnetic measurements at ultimate spatial resolution with electrons

MA 26.4: Hauptvortrag

Mittwoch, 18. März 2015, 11:15–11:45, EB 202

Utilizing chirality to explore local magnetic moments — •Peter Schattschneider — Institute of Solid State Physics, Vienna University of Technology, Vienna, Austria

Energy loss magnetic chiral dichroism (EMCD) is a rather new approach to study element specific magnetic moments with highest spatial resolution. EMCD is detected as an asymmetry in the transition probability to states with positive or negative magnetic quantum numbers (chiral transitions). The technique is similar to its well established relative, X-ray magnetic circular dichroism (XMCD) where the asymmetry appears in the fine structure of ionisation edges of magnetic materials. The observation that chiral electronic transitions break certain mirror symmetries in energy spectroscopic diffraction (ESD) led to the prediction that this breaking pertains in energy filtered high resolution imaging, thus opening the road to mapping spins of individual atomic columns under high resolution conditions in a conventional TEM. This was experimentally demonstrated on magnetite. An important advantage over XMCD is the site specificity, enabling the study of ferri- and antiferromagnets.

One of the intriguing consequences of EMCD is that the outgoing probe electrons have topological charge. Such electrons carry quantized orbital angular momentum, similar to the recently discovered vortex electrons. Vice versa, vortex electrons are a promising probe for atomic resolution spin mapping.

The author acknowledges funding from the Austrian Science Fund, project no. I543-N20