Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 34: Poster Session
MM 34.37: Poster
Dienstag, 1. April 2014, 18:00–20:00, P4
STEM with focused vortex beams - a route towards local EMCD measurements? — •Darius Pohl1, Sebastian Schneider1,2, Ludwig Schultz1,2, and Bernd Rellinghaus1 — 1IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany — 2TU Dresden, Institut fur Festkörperphysik, D-01062 Dresden, Germany
X-ray magnetic circular dichroism is a well established method to study element specific magnetic properties of a material, while electron magnetic circular dichroism (EMCD), which is the electron wave analogue to XMCD, is scarcely used today. Recently discovered electron vortex beams, which carry a discrete orbital angular momentum (OAM) L, are predicted to also reveal dichroic signals. Since electron beams can be easily focused down to sub-nanometer diameters, this novel technique provides the possibility to quantitatively determine local magnetic properties with unrivalled lateral resolution. As the spiralling wave front of the electron vortex beam has an azimutally growing phase shift of up to 2π and a phase singularity in its axial center, specially designed apertures are needed to generate such non-planar electron waves. We report on the preparation and successful implementation of spiral apertures into the condenser lens system of an aberration-corrected FEI Titan3 80-300 transmission electron microscope (TEM). This setup allows to perform scanning TEM (STEM) with vortex beams carrying user-selected OAM. First experiments and simulations on the interaction of the vortex beam with a crystalline sample will be presented.