Considering the growing interest in magnetic materials for unconventional computing, data storage, and sensor applications, there is active research not only on material synthesis but also characterisation of their properties. In addition to structural and integral magnetic characterisations, imaging of magnetisation patterns, current distributions and magnetic fields at nano- and microscale is of major importance to understand the material responses and qualify them for specific applications. In this roadmap, we aim to cover a broad portfolio of techniques to perform nano- and microscale magnetic imaging using superconducting quantum interference devices, spin centre and Hall effect magnetometries, scanning probe microscopies, x-ray- and electron-based methods as well as magnetooptics and nanoscale magnetic resonance imaging. The roadmap is aimed as a single access point of information for experts in the field as well as the young generation of students outlining prospects of the development of magnetic imaging technologies for the upcoming decade with a focus on physics, materials science, and chemistry of planar, three-dimensional and geometrically curved objects of different material classes including two-dimensional materials, complex oxides, semi-metals, multiferroics, skyrmions, antiferromagnets, frustrated magnets, magnetic molecules/nanoparticles, ionic conductors, superconductors, spintronic and spinorbitronic materials.

Magnetic skyrmions are chiral spin textures which have attracted intense research for their fundamentally novel physics and potential applications as spintronic information carriers. The stability which makes them so potentially useful is a result of their underlying nontrivial topology. While skyrmions were originally predicted and observed in crystalline materials lacking inversion symmetry, some of the most promising host systems for skyrmions are multilayer thin films, where skyrmions have been stabilized at ambient conditions, which is critical for their use in real-world devices. The skyrmions found in multilayer thin films have additional three-dimensional structure, with their domain wall helicities twisting through the thickness of the film to create a hybrid skyrmion composed of a Bloch-type core with N & eacute;el-type caps of opposite chiralities at the surfaces. In this paper, we show that this three-dimensional variation creates additional knotted topological structure, providing an explanation for their exceptional stability in ambient conditions. We show that hybrid skyrmions can be described as half-integer hopfions, and that their field lines have the knotted structure of the Hopf fibration. Furthermore, we show that the topological charge of partially twisted hybrid skyrmions can be related to the domain wall helicity at the surfaces, providing a straightforward way to connect experimental measurements to underlying topology.

It is often assumed that electron backscatter and continuum (bremsstrahlung) productions emitted from electron-solid interactions during X-ray microanalysis in compounds can be extrapolated from pure element observations by means of the assumption of average atomic number, or Z-bar (Z¯). For pure elements the average Z is equal to the atomic number, but this direct approach fails for compounds. The use of simple atomic fractions yields completely spurious results, and while the commonly used mass fraction Z averaging produces fairly reasonable results, we know from physical considerations that the mass of the neutron plays only a negligible role in such interactions below ∼1 MeV. Therefore, including the mass or atomic weight in such calculations can only introduce further errors in these models. We present an expression utilizing atomic fractions of the atomic numbers of the elements in the compound (Z fraction), with an exponent to account for the variation in nuclear screening as a function of the element Z value.

Journal Article Measuring Phase and Symmetries in STEM-EELS Get access Benjamin J McMorran, Benjamin J McMorran Department of Physics, University of Oregon, Eugene, Oregon, USA Corresponding author: mcmorran@uoregon.edu Search for other works by this author on: Oxford Academic Google Scholar Cameron W Johnson, Cameron W Johnson Department of Physics, University of Oregon, Eugene, Oregon, USANational Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA Search for other works by this author on: Oxford Academic Google Scholar Amy E Turner Amy E Turner Department of Physics, University of Oregon, Eugene, Oregon, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 374–375, https://doi.org/10.1093/micmic/ozad067.175 Published: 22 July 2023

Understanding magnetic phase transitions from stripe to skyrmion textures provide fundamental scientific insights into the details of the intermediate topologies through which the system evolves. The solitonic nature of spin texture in both stripe and skyrmion phases has been observed in materials with Dzyaloshinskii-Moriya interaction. Here we show that the field evolution in a dipolar interaction mediated Fe/Gd multilayer that exhibits achiral stripe textures behaves similar to a finite-sized chiral soliton lattice. As a function of magnetic field, the stripes exhibit discrete jumps in periodicity indicative of intermediate topologies as the stripes get wound into skyrmions.

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We use a novel scanning electron Mach-Zehnder interferometer constructed in a conventional transmission electron microscope to perform inelastic interferometric imaging with free electrons. An electron wave function is prepared in two paths that pass on opposite sides of a gold nanoparticle, where plasmons are excited before the paths are recombined to produce electron interference. We show that the measured spectra are consistent with theoretical predictions, specifically that the interference signal formed by inelastically scattered electrons is π out of phase with respect to that formed by elastically scattered electrons. This technique is sensitive to the phase of localized optical modes, because the interference signal amounts to a substantial fraction of the transmitted electrons. Thus, we argue that inelastic interferometric imaging with our scanning electron Mach-Zehnder interferometer provides a new platform for controlling the transverse momentum of free electrons and studying coherent electron-matter interactions at the nanoscale.

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Journal Article Electron Microscopy Spin Analysis of Topological Magnetic Domains in Amorphous Fe/Gd Thin Films Get access Rich Moraski, Rich Moraski Department of Physics, University of Oregon, Eugene, OR, USA Corresponding author: rmoraski@uoregon.edu Search for other works by this author on: Oxford Academic Google Scholar Ian Gilbert, Ian Gilbert Seagate Research, Seagate Technology, Shakopee, MN, USA Search for other works by this author on: Oxford Academic Google Scholar Sergio A Montoya, Sergio A Montoya Center for Memory and Recording Research, University of California San Diego, La Jolla, CA, USA Search for other works by this author on: Oxford Academic Google Scholar Eric E Fullerton, Eric E Fullerton Center for Memory and Recording Research, University of California San Diego, La Jolla, CA, USA Search for other works by this author on: Oxford Academic Google Scholar Benjamin J McMorran Benjamin J McMorran Department of Physics, University of Oregon, Eugene, OR, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 1688–1689, https://doi.org/10.1017/S1431927622006717 Published: 01 August 2022

We demonstrate a two-grating free electron Mach-Zehnder interferometer constructed in a transmission electron microscope. A symmetric binary phase grating and a condenser lens system form two spatially separated, focused probes at the sample which can be scanned while maintaining alignment. The two paths interfere at a second grating, creating constructive or destructive interference in the output beams. This interferometer has many notable features: positionable probe beams, large path separations relative to beam width, continuously tunable relative phase between paths, and real-time phase information. Here we use the electron interferometer to measure the relative phase shifts imparted to the electron probes by electrostatic potentials as well as a demonstration of quantitative nanoscale phase imaging of a polystyrene latex nanoparticle.

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Here, we experimentally demonstrate interaction-free measurements with electrons using a novel electron Mach-Zehnder interferometer. The flexible two-grating electron interferometer is constructed in a conventional transmission electron microscope and achieves high contrast in discrete output detectors, tunable alignment with independently movable beam splitters, and scanning capabilities for imaging. With this path-separated electron interferometer, which closely matches theoretical expectations, we demonstrate electron interaction-free measurements with an efficiency of 14±1%. Implementing this quantum protocol in electron imaging opens a path toward interaction-free electron microscopy.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.