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MA: Fachverband Magnetismus
MA 26: Focus: Towards quantitative magnetic measurements at ultimate spatial resolution with electrons
MA 26.6: Talk
Wednesday, March 18, 2015, 12:15–12:30, EB 202
EMCD measurements on ferromagnetic nanoparticles using electron vortex probes — •Darius Pohl1, Sebastian Schneider1,2, Jan Rusz3, Peter Tiemeijer4, and Bernd Rellinghaus1 — 1IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany — 2TU Dresden, Institute for Solid State Physics, D-01062 Dresden, Germany — 3Uppsala University, Department of Physics and Astronomy, SE-752 37 Uppsala, Sweden — 4FEI Company, PO Box 8066, 5600 KA Eindhoven, The Netherlands
Recently discovered electron vortex beams, which carry a discrete orbital angular momentum (OAM) L, are predicted to 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 and dislocation 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 vortex beams with ferromagnetic FePt nanoparticles reveal both the potential and present limitations of this technique.