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Magnetism arises from the angular momentum of charges. Electrons therefore provide a useful probe to measure and image magnetic fields. For example, the most common magnetic electron microscopy techniques, Lorentz TEM and differential phase contrast (DPC) microscopy, can be used to quantitatively image the average magnetic field projected through a thin magnetic sample under varying external conditions, such as during an applied field sweep or temperature variation. We use Lorentz TEM to investigate magnetic topological spin textures iron-based thin films. Under the right conditions, we observe skyrmions, which are knots of magnetization forming a pseudoparticle that have potential for new forms of information storage and computation. We see evidence for a three-dimensional structure for these skyrmions that hints at a higher level of topology, which could have implications for the topological Hall effect within these thin films. We developed and applied to more electron microscopy techniques to confirm this structure: electron interferometry and surface-sensitive scanning electron microscopy with polarization analysis (SEMPA). I will introduce these techniques, and discuss how they are being applied to provide more complete pictures of 3D magnetic skyrmions.
Benjamin McMorran is Associate Professor of Physics at the University of Oregon. His research interests are free electron physics and interferometry, matter wave optics, electron microscopy, magnetic materials. He did post-doctoral work in the Electron Physics Group, CNST, NIST, Gaithersburg, MD. He has a Ph.D. in Physics from the University of Arizona, and a B.S. in Physics from Oregon State Unviersity - we'e proud to welcome back our alum!