X-ray linear dichroism has been pivotal for probing electronic anisotropies, but its inherent limited spatial resolution precludes atomic-scale investigations of orbital polarization. Here we introduce a versatile electron linear dichroism methodology in scanning transmission electron microscopy that overcomes these constraints. By exploiting momentum-transfer-dependent electron energy-loss spectroscopy with an atomic-sized probe, we directly visualize orbital occupation at individual atomic columns in real space. Using strained La0.7Sr0.3MnO3 thin films as a model system, we resolve the Mn-3d eg orbital polarization with sub-angstrom precision. We show that compressive strain stabilizes 3z2-r2 occupation while tensile strain favors x2-y2. These results validate our approach against established X-ray measurements while achieving the ultimate single atomic-column sensitivity. We further demonstrate two optimized signal extraction protocols that adapt to experimental constraints without compromising sensitivity. This generalizable platform opens unprecedented opportunities to study symmetry-breaking phenomena at individual defects, interfaces, and in quantum materials where atomic-scale electronic anisotropy governs emergent functionality.

Chalcogenide spinels exhibit electronic and magnetic properties that are tunable through lattice occupancy and composition. Here, we report the first synthesis of spinel-phase Ag2Cr2Se4 and AgCr2Se4 and demonstrate an oxidation-induced ferro-to-ferrimagnetic transition accompanied by a massive increase in TC of >250 K associated with changes in Ag+ site occupancy. The Ag spinels are synthesized through air-free cation exchange of CuCr2Se4 nanocrystals driven by excess AgNO3 to yield ferromagnetic Ag2Cr2Se4 (a = 10.838(4) Å, TC = 152 K, 2 K saturation = 3.1 μB/Cr) with Ag+ occupying both Td 8a and Oh 16c sites. Upon air exposure, Ag2Cr2Se4 converts to ferrimagnetic AgCr2Se4 (a = 10.6085(19) Å, TC > 400 K, 2 K saturation = 2.2 μB/Cr) through a loss of Oh-Ag+ alongside the formation of Ag2Se. We attribute the ferro-to-ferrimagnetic transition to the generation of holes in Ag-Se bands, which couple antiferromagnetically to Cr3+. This Ag-Cr-Se spinel system demonstrates the largest change in TC reported and provides an excellent framework for further exploration of magnetic coupling as a function of oxidation and structure.

The negatively charged boron vacancy (V-B(-) ) in hexagonal boron nitride (hBN) is a promising quantum defect that can be used to sense pressure, temperature, and magnetic field with high spatial resolution. hBN enriched with the boron-10 and nitrogen-15 isotopes, denoted h(10)B(15)N, has good contrast and coherence for quantum sensing because nitrogen-15 has nuclear spin (1/2), reducing hyperfine interactions. Boron vacancies can be generated by neutron irradiation, which causes the transmutation of the boron-10 isotope to lithium-7. In this study, the ancillary structural, compositional, and mechanical properties of h(10)B(15)N crystals that have been subjected to neutron irradiation fluences from 1.4 & times; 10(16) to 8.4 & times; 10(17) n/cm(2) were thoroughly characterized. Besides creating V-B(-) , the process also induces other defects that generate strain in the crystal lattice. In turn, the mechanical properties of these crystals change drastically. Investigated here are the visual changes, lattice integrity, composition, crystal strain, and elastic constants (C-33 and C-66) to assess how these characteristics change as a function of neutron fluence.

The recent discovery of altermagnetism has sparked growing interest in compensated magnetic systems as promising platforms for highly scalable spintronics. Altermagnetism is a distinct magnetic order where opposite spin sublattices are connected by rotation, yielding zero net magnetization but momentum-dependent spin splitting. To date, experimental verification of altermagnetic order has been achieved predominantly through bulk-sensitive techniques, including spin-dependent electronic spectra and transport responses. However, direct atomic-scale evidence that explicitly correlates crystal symmetry, local structural distortions, and magnetic ordering has remained unexplored. Here, we report the direct atomic-scale observation of coexisting polar distortions and altermagnetic order in MnTe, combining atomic resolution scanning transmission electron microscopy (STEM) imaging with electron magnetic chiral dichroism (EMCD) measurements. We reveal that MnTe is not an ideal uniform P63/mmc g-wave altermagnet at the atomic scale. Instead, it hosts ubiquitous inversion-symmetry-breaking distortions that lower the spin-space-group (SSG) symmetry, admits d-wave altermagnetic components, and in lower-symmetry regimes, even allow s-wave spin splitting (net magnetization). The coexistence of ferroelectric signatures and altermagnetic order establishes local lattice symmetry in MnTe as a control knob for altermagnetic spin splitting, spin current generation, and multiferroic memory applications.

The miniaturization of transistors is approaching its limits owing to challenges in heat management and information transfer speed1. To overcome these obstacles, emerging technologies such as spintronics2 are being developed, which make use of the electron's spin as well as its charge. Local phenomena at interfaces or structural defects will greatly influence the efficiency of spin-based devices, making the ability to study spin-wave propagation at the nanoscale and atomic scale a key challenge3,4. The development of high-spatial-resolution tools to investigate spin waves, also called magnons, at relevant length scales is thus essential to understand how their properties are affected by local features. Here we detect bulk THz magnons at the nanoscale using scanning transmission electron microscopy (STEM). By using high-resolution electron energy-loss spectroscopy with hybrid-pixel electron detectors, we overcome the challenges posed by weak signals to map THz magnon excitations in a thin NiO nanocrystal. Advanced inelastic electron scattering simulations corroborate our findings. These results open new avenues for detecting magnons and exploring their dispersions and their modifications arising from nanoscale structural or chemical defects. This marks a milestone in magnonics and presents exciting opportunities for the development of spintronic devices.

Fluids under extreme confinement exhibit unique structures and intermolecular bonding, distinct from their bulk analogs, driving innovative applications at the water-energy nexus. Probing confined water experimentally at the length scale of intermolecular and surface forces has, however, remained a challenge. Here, we report direct molecular-level observations of hydrogen bonding in water confined inside individual carbon nanotubes, enabled by in-situ vibrational electron energy-loss spectroscopy with nanoscale resolution. Hydrogen bonding is probed via the intramolecular O-H stretching frequency, which serves as a sensitive spectral signature of the local intermolecular bonding environment. Water in larger carbon nanotubes exhibit the bonded O-H vibrations of bulk water, but at smaller diameters, the frequency blueshifts to near the free O-H stretch found in water vapor and hydrophobic surfaces, indicating a highly dispersed, non-H-bonded environment. Theoretical analysis based on quantum vibrational oscillators indicates that enhanced damping rates, corresponding to rapid hydrogen-bond fluctuations, leads the bimodal spectral peaks to merge into a single broad feature, matching the experimental observation. Furthermore, cryogenic experiments provide insights into complex structural phase transitions of confined water. This research reveals the quantum and dynamic nature of hydrogen bonds under confinement and the potential impact of unveiling molecular-level structure and bonding in confined fluids.

Conversion of charge to orbital angular momentum through the orbital Hall effect (OHE) holds transformative potential for the development of orbital-based electronics, however, it is challenging to directly observe the electrically generated orbital accumulation. Here, we detect the OHE by directly quantifying the orbital accumulation along the edges of a titanium thin film using a scanning transmission electron microscope. We measure the Ti L-edge using electron energy-loss spectroscopy with nanometer resolution and find a sizable orbital accumulation at the sample's outer perimeters, consistent with all signatures expected for the OHE, and determine an orbital diffusion length $\ell_o \approx 7.3$ nm. Our data points to a surprising dependence of the orbital diffusion length on the nano-structural morphology.

Antiferroelectricity is a material property characterized by alternating electric dipoles spontaneously ordered in antiparallel directions. Antiferroelectrics are promising for energy storage, solid-state cooling, and memory technologies; however, these materials are scarce, and their scalability remains largely unexplored. In this work, we demonstrate that single-crystalline hafnia, a lead-free CMOS-compatible material, exhibits antiferroelectricity under compressive-strain conditions. We observe antiparallel sublattice polarization and stable double-hysteresis in single-crystalline (111)-oriented epitaxial La-doped hafnia films grown on yttrium-stabilized zirconia and show that the antipolar orthorhombic phase of hafnia adheres to the Kittel model of antiferroelectricity. Notably, compressive strain strengthens the antiferroelectric order in thinner La-doped hafnia films, achieving an unprecedented 850 C ordering temperature in the two-dimensional limit, highlighting hafnia's potential for advanced antiferroelectric devices.

Plasmonic lattice nanostructures are of technological interest because of their capacity to manipulate light below the diffraction limit. Here, we present a detailed study of dark and bright modes in the visible and near-infrared energy regime of an inverted plasmonic honeycomb lattice by a combination of Au+ focused ion beam lithography with nanometric resolution, optical and electron spectroscopy, and finite-difference time-domain simulations. The lattice consists of slits carved in a gold thin film, exhibiting hotspots and a set of bright and dark modes. We proposed that some of the dark modes detected by electron energy-loss spectroscopy are caused by antiferroelectric arrangements of the slit polarizations with two times the size of the hexagonal unit cell. The plasmonic resonances take place within the 0.5-2 eV energy range, indicating that they could be suitable for a synergistic coupling with excitons in two-dimensional transition metal dichalcogenides materials or for designing nanoscale sensing platforms based on near-field enhancement over a metallic surface.

Journal Article Revealing Atomic Structure, Strain and Moiré-Exciton Coupling of hBN/WSe2/WS2 Superlattice at LN2 Temperature by Monochromated EELS and ADF-STEM Imaging Get access Elizaveta Tiukalova, Elizaveta Tiukalova Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, United States Corresponding author: tiukalovae@ornl.gov Search for other works by this author on: Oxford Academic Google Scholar Yuzhou Zhao, Yuzhou Zhao Department of Physics, University of Washington, Seattle, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Jihui Yang, Jihui Yang Materials Science & Engineering Department, University of Washington, Seattle, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Xiaodong Xu, Xiaodong Xu Department of Physics, University of Washington, Seattle, WA, United StatesMaterials Science & Engineering Department, University of Washington, Seattle, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Andrew R Lupini, Andrew R Lupini Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, United States Search for other works by this author on: Oxford Academic Google Scholar Juan Carlos Idrobo Juan Carlos Idrobo Materials Science & Engineering Department, University of Washington, Seattle, WA, United StatesPhysical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 1707–1708, https://doi.org/10.1093/micmic/ozad067.881 Published: 22 July 2023