Electron microscopy touches on nearly every aspect of modern life, underpinning materials development for quantum computing, energy and medicine. We discuss the open, highly integrated and data-driven microscopy architecture needed to realize transformative discoveries in the coming decade.

Thin-film oxide heterostructures show great potential for use in spintronic memories, where electronic charge and spin are coupled to transport information. Here we use a La 0.7 Sr 0.3 MnO 3 (LSMO)/PbZr 0.2 Ti 0.8 O 3 (PZT) model system to explore how local variations in electronic and magnetic phases mediate this coupling. We present direct, local measurements of valence, ferroelectric polarization and magnetization, from which we map the phases at the LSMO/PZT interface. We combine these experimental results with electronic structure calculations to elucidate the microscopic interactions governing the interfacial response of this system. We observe a magnetic asymmetry at the LSMO/PZT interface that depends on the local PZT polarization and gives rise to gradients in local magnetic moments; this is associated with a metal-insulator transition at the interface, which results in significantly different charge-transfer screening lengths. This study establishes a framework to understand the fundamental asymmetries of magnetoelectric coupling in oxide heterostructures.

Magnetoelectric oxide heterostructures are proposed active layers for spintronic memory and logic devices, where information is conveyed through spin transport in the solid state. Incomplete theories of the coupling between local strain, charge, and magnetic order have limited their deployment into new information and communication technologies. In this study, we report direct, local measurements of strain- and charge-mediated magnetization changes in the La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 system using spatially resolved characterization techniques in both real and reciprocal space. Polarized neutron reflectometry reveals a graded magnetization that results from both local structural distortions and interfacial screening of bound surface charge from the adjacent ferroelectric. Density functional theory calculations support the experimental observation that strain locally suppresses the magnetization through a change in the Mn-eg orbital polarization. We suggest that this local coupling and magnetization suppression may be tuned by controlling the manganite and ferroelectric layer thicknesses, with direct implications for device applications.

This article investigates a facile one-pot method for the synthesis of Fe and Ag core/shell nanoparticles by aqueous reduction under ambient conditions. We have shown that the injection time of silver nitrate into a reaction vessel containing aqueous ferrous salt, sodium borohydride, and sodium citrate is a vital parameter for the precise control of a desired core/shell structure. For example, if silver nitrate is injected one minute after sodium borohydride is added to the reaction vessel, Ag will nucleate first followed by Fe, creating monodisperse Ag/Fe core/shell nanoparticles. In contrast, if the introduction time is prolonged to 5 min, Fe nanoparticles will nucleate followed by Ag producing Fe/Ag nanoparticles. The composition, morphology, and magnetic behavior were investigated by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and room-temperature vibrating sample magnetometry (VSM). Fe/Ag core/shell nanoparticles with optical and magnetic functionality offer broad opportunities in medicine, catalysis, and chemical detection.

The polarity of oxide surfaces can dramatically impact their surface reactivity, in particular with polar molecules such as water. The surface species that result from this interaction change the oxide electronic structure and chemical reactivity in applications such as 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 photoelectrochemistry, but are challenging to probe experimentally. Here we report a detailed study of the surface chemistry and electronic structure of the perovskite LaFeO 3 in humid conditions using ambient pressure X-ray photoelectron spectroscopy. Comparing the two possible terminations of the polar (001)-oriented surface, we find that the LaO-terminated surface is more reactive toward water, forming hydroxyl species and adsorbing molecular water at lower relative humidity than its FeO 2 -terminated counterpart. However, the FeO 2 -terminated surface forms more hydroxyl species during water adsorption at higher humidity, suggesting adsorbate-adsorbate interactions may impact reactivity. Our results demonstrate how the termination of a complex oxide can dramatically impact its reactivity, providing insight that can aid in the design of catalyst materials. TOC GRAPHICSPerovskite oxides such as LaFeO 3 show great promise as catalysts for energy conversion and storage. Applications such as electrocatalysis, 1-4 photoelectrochemistry, 5-7 and gas sensing 8-10 all take place in an aqueous or humid environment, where the interaction with water plays a key role in determining the functionality of these complex oxides. [11][12][13] The formation of surface hydroxyl groups and adsorption of water can impact the surface electronic structure 14 and ultimately the mechanisms and kinetics of surface chemical reactions. 15,16 Initial studies have considered the reactivity of perovskites with water using ambient pressure X-ray photoelectron spectroscopy 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 (AP-XPS), 12,17 enabling study of the surface species present in equilibrium with water vapor. The hydroxylation of these surfaces appeared greater than that of binary transition metal oxides. 18However, the chemical nature of the hydroxyl site in such systems remained elusive due to the unknown surface termination.The polar layers of (001) Figure 1, confirm the excellent quality and epitaxy of the film. We observe differences in the surface termination, although damage resulting from TEM sample preparation makes it difficult to unambiguously identify the surface layer. Instead, the termination of the as-prepared film was confirmed by angle resolved XPS (Table S1) and remained unchanged during AP-XPS experiments ( Figure S2). 5TiO 2 -te...