Figure. (a) FeGe tetrahedron on a tip, (b) Calculated phase map and its projections, (c) comparison of experimental and simulated magnetic-phase projections.Fig. 1 Schematic of the experimental method.77P4-11Observation of Skyrmionic Vortex Using Electron Holography Kodai NiitsuCenter for Basic Research on Materials, National Institute for Materials Science (NIMS)The topological magnetic structure stabilized in a tetrahedral nanoparticle of B20-structure FeGe, a material hosting magnetic skyrmions, was determined. Using electron holography, magnetic-phase projections were obtained from multiple directions for one nanoparticle, and by integrating coupled analysis of micromagnetic simulation and finite element integration, the phase changes integrated across the same directions were calculated and imaged. As a result, it was found that the magnetic texture shapes a vortex structure with a spherical outline due to the chiral geometric frustration, which was named a skyrmionic vortex (see Figure).P4-12Direct Imaging of Thermal Vibration Modes Using Frequency-Selective Electron MicroscopyOvidiu Cretu, Han Zhang, and Koji KimotoCenter for Basic Research on Materials, National Institute for Materials Science (NIMS)In the absence of a driving force, objects experience thermal vibration, solely due to their non-zero temperature. Spatially resolved measurements of these vibrations are limited by their small amplitudes and by the overlap between different modes. We have developed a technique [1] which combines the extremely high spatial resolution of a STEM and fast signal acquisition electronics, which can display several thermal vibration [1] O. Cretu et al., Nano Lett., 22, 10034–10039 (2022).This study was conducted in collaboration with Y. Liu, X. Yu, D. Shindo, N. Nagaosa, Y. Tokura (from RIKEN), A. C. Booth, S. Jin (from U. New Hampshire), and N. Mathur, M. Stolt, J. Zang (from Univ. Wisconsin-Madison)[1] K. Niitsu et al., Nature Materials, 21, 305-310 (2022).modes simultaneously, with nanometer resolution.This is showcased by mapping the first few thermal vibration modes of a nanowire, which agree well with classical vibration theory and FEM simulations. The influence of temperature on the vibration process as well as progress towards acquiring direct stroboscopic images of the vibration will also be discussed.This work was supported by JSPS KAKENHI grants JP20H02624, JP22H05145, and JP24K08253.
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