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Oil spill contamination occurs due to exploration activities in the deep sea and downstream activities such as oil transportation via pipelines, oil-tankers (marine and terrestrial), re-fineries, finished product storage, distribution, and retail distribution setup. Physico-chemical technologies are accessible for oil spill clean-up, but oil bioremediation technologies are proven to be more affordable and environmentally friendly. The aim of this book chapter is to give deeper knowledge about the bioremediation technology of oil spills. This chapter discusses the nature and composition of crude oil, bioremediation agents and strategies, bioremediation on different matrices (water, soil sludge), application strategy, and future prospect of bioremediation technology.

The most problematic issue related to textile wastewater is dyes. The occurrence of toxic and carcinogenic compounds in textile dyes creates aesthetic problems and affects the aquatic ecosystem. Dyestuff removal methods include physical, chemical, and biological-based technology. For a more environmentally friendly process that is low cost, produces less sludge, and needs a lesser amount of chemicals, biological treatment is preferable technology. To get maximum effectiveness and efficiency, integrations/ hybrids consisting of several technologies are commonly used. This chapter is dedicated to exploring the potential of biological technology to remove dyes from wastewater, especially dyes used in textile industries. This chapter briefly discusses dyes' characteristics, their utilization, and toxicity. Deeper reviews about the biodegradation potential of dyes are elaborated, along with a discussion about biodegradation mechanisms and reviews of either lab-scale or full-scale applications of biological-based technology for dyes treatment. Lastly, this chapter also gives future insight into the biological treatment of dyes.&nbsp

Topological spin textures are of great interest for both fundamental physics and applications in spintronics. The Dzyaloshinskii–Moriya interaction underpins the formation of single-twisted magnetic solitons or multi-twisted magnetic skyrmions in magnetic materials with different crystallographic symmetries. However, topological transitions between these two kinds of topological objects have not been verified experimentally. Here, the direct observation of transformations from a chiral soliton lattice (CSL) to magnetic skyrmions in a nanostripe of the monoaxial chiral magnet CrNb3S6 using Lorentz transmission electron microscopy is reported. In the presence of an external magnetic field, helical spin structures first transform into CSLs and then evolve into isolated elongated magnetic skyrmions. The detailed spin textures of the elongated magnetic skyrmions are resolved using off-axis electron holography and are shown to comprise two merons, which enclose their ends and have unit total topological charge. Magnetic dipolar interactions are shown to play a key role in the magnetic soliton–skyrmion transformation, which depends sensitively on nanostripe width. The findings here, which are consistent with micromagnetic simulations, enrich the family of topological magnetic states and their transitions and promise to further stimulate the exploration of their emergent electromagnetic properties.

Objectives After bonding brackets to the first deciduous molar in a 2 × 4 technique, a three-dimensional finite element analysis (3D FEA) is used to demonstrate the biomechanical changes in an orthodontic system. This study aims to opt for the appropriate type of orthodontic technology by analyzing and comparing the mechanical systems produced by two types of 2 × 4 technologies employing rocking-chair archwires. Materials and methods Herein, maxilla and maxillary dentition are modeled by cone beam computed tomography (CBCT) and 3D FEA. Common clinically used round titanium-molybdenum alloy archwires (diameter: 0.016’’ and 0.018’’) and round stainless-steel archwires (diameter: 0.016’’ and 0.018’’) are bent into the shape of a rocking chair with a depth of 3 mm. The forces and moments applied to the brackets are transferred to the dentition to evaluate the biomechanical effects of the 2 × 4 technique after the bracket is bonded to the first deciduous molar. Results When using the same size and orthodontic technique, the forces and moments applied to the teeth by the rocking-chair stainless-steel archwire are approximately three times those applied by the rocking-chair titanium-molybdenum alloy archwire. Therefore, this study investigates only the initial movements of teeth and periodontal ligaments using round stainless-steel archwires. The left-hand side of the patient is defined as the positive X-axis direction, rear as the positive Y-axis direction, and top as the positive Z-axis direction. For the central incisor, the teeth-moving distance in all three directions increases with the bracket bonding to the first deciduous molar using the 0.016’’ rocking-chair archwire. No significant differences between the two orthodontic methods using a 0.018’’ archwire are observed. For the lateral incisor, the tooth root moves toward the gingival side when using 0.016’’ and 0.018’’ archwires. Moreover, for the same archwire size, the lateral incisors move toward the gingival side by bonding the bracket to the first deciduous molar, which is conducive to the anterior teeth intrusion. For the first molar, using rocking-chair 0.016’’ or 0.018’’ archwires, after the bracket is bonded to the first deciduous molar, in the X-axis direction, the buccal movement distance of the first molar crown increases. In the Y-axis and Z-axis directions, the modified 2 × 4 technology significantly increases the effect of backward-tipping compared with the traditional 2 × 4 technology; thus, the modified 2 × 4 technology considerably reduces the anchorage loss. Conclusions In clinical practice, the modified 2 × 4 technology can be used to increase the movement distance of anterior teeth to a certain extent and accelerate the orthodontic teeth movement. Moreover, the modified 2 × 4 technology is better in anchorage conversation of the first molar than the traditional technology.

High-precision piezo actuators necessitate dielectrics with high electrostrain performance with low hysteresis. Polarity-modulated (Sr

Lead-free relaxor ferroelectric ceramics with ultrahigh energy-storage performance are vital for pulsed power systems. We herein propose a strategy of phase and band structure engineering for high-performance energy storage. To demonstrate the effectiveness of this strategy, (1

The construction of island airports on coral reefs inevitably encounters the impact load of aircraft takeoff and landing. However, previous studies have not presented a detailed description of the dynamic response of the coral sand beneath the runways of island reclamation airports under aircraft load. In the current study, the coral sand of Mischief Reef Airport in the Nansha Islands, China, was selected as the background. The pore water pressure and strain characteristics of reshaped coral sand under aircraft loads with different dynamic stress amplitudes and vibration frequencies were studied using dynamic triaxial tests. Particle discrete element software was employed to study the deformation characteristics of coral sand with different particle sizes and porosities under aircraft loads. Results show that when the dynamic stress amplitude and vibration frequency were small, the pore water pressure and strain of the coral sand samples gradually increased with the number of load cycles, and the growth rate became increasingly small. When the dynamic stress amplitude and vibration frequency were large, the axial strain of the coral sand samples increased with the vibration frequency, and the growth rate exhibited an increasing trend. The deformation of the coral sand samples increased with porosity under aircraft loading. The larger the variation range of the coral sand particle size was, the larger the coral sand deformation caused by aircraft takeoff and landing load was. These results can provide a reference for the treatment and repair of the airstrip foundation of island airports.

Fe-based superconductors are one of the current research focuses. FeTe is unique in the series of FeSe1−x Te x , since it is nonsuperconducting near the FeTe side in the phase diagram in contrast to the presence of superconductivity in other region. However, FeTe thin films become superconducting after oxygen annealing and the mechanism remains elusive. Here, we report the temperature dependences of resistivity, Hall effect and magnetoresistance (MR) of a series of FeTe thin films with different amounts of excess Fe and oxygen. These properties show dramatic changes with excess Fe and oxygen incorporation. We found the Hall coefficients are positive for the oxygen-annealed samples, in contrast to the transition from positive to negative below 50 K for the vacuum-annealed samples. For all samples, both the resistivity and Hall coefficient show a dramatic drop, respectively, at around 50 K–75 K, implying coexistence of superconductivity and antiferromagnetic order for the oxygen-annealed samples. The vacuum-annealed samples show both positive and negative values of MR depending on temperature, while negative MR dominates for the oxygen-annealed samples. We also found that oxygen annealing reduces the excess Fe in FeTe, which has been neglected before. The results are discussed in terms of several contributions, and a comparison is made between the oxygen-annealed FeTe thin films and FeSe1−x Te x . This work is helpful for shedding light on the understanding of oxygen-annealed FeTe thin films.

The flexoelectric effect, which manifests itself as a strain-gradient-induced electrical polarization, has triggered great interest due to its ubiquitous existence in crystalline materials without the limitation of lattice symmetry. Here, we propose a flexoelectric photodetector based on a thin-film heterostructure. This prototypical device is demonstrated by epitaxial LaFeO3 thin films grown on LaAlO3 substrates. A giant strain gradient of the order of 106/m is achieved in LaFeO3 thin films, giving rise to an obvious flexoelectric polarization and generating a significant photovoltaic effect in the LaFeO3-based heterostructures with nanosecond response under light illumination. This work not only demonstrates a novel self-powered photodetector different from the traditional interface-type structures, such as the p–n and Schottky junctions but also opens an avenue to design practical flexoelectric devices for nanoelectronics applications.

A Bi2Te3/Bi2S3@Bi nanocomposite with a network microstructure was successfully synthesized via a hydrothermal method and spark plasma sintering. This composite was constructed from Bi2Te3 nanoparticles and Bi2S3@Bi nanowires, and its network structure is beneficial for obtaining excellent thermoelectric performance. A ZT peak of 1.2 at 450 K was realized for the nanocomposite sample.

Grain boundaries could exhibit exceptional electronic structure and exotic properties, which are determined by a local atomic configuration and stoichiometry that differs from the bulk. However, optical and plasmonic properties at the grain boundaries in metallic oxides have rarely been discussed before. Here, we show that non-stoichiometric grain boundaries in the newly discovered metallic SrNbO3 photocatalyst show exotic electronic, optical and plasmonic phenomena in comparison to bulk. Aberration-corrected scanning transmission electron microscopy and first-principles calculations reveal that a Nb-rich grain boundary exhibits an increased carrier concentration with quasi-1D metallic conductivity, and newly induced electronic states contributing to the broad energy range of optical absorption. More importantly, dielectric function calculations reveal extended and enhanced plasmonic excitations compared with bulk SrNbO3. Our results show that non-stoichiometric grain boundaries might be utilized to control the electronic and plasmonic properties in oxide photocatalysis.

Writing, erasing and computing are three fundamental operations required by any working electronic devices. Magnetic skyrmions could be basic bits in promising in emerging topological spintronic devices. In particular, skyrmions in chiral magnets have outstanding properties like compact texture, uniform size and high mobility. However, creating, deleting and driving isolated skyrmions, as prototypes of aforementioned basic operations, have been grand challenge in chiral magnets ever since the discovery of skyrmions, and achieving all these three operations in a single device is highly desirable. Here, by engineering chiral magnet Co$_8$Zn$_{10}$Mn$_2$ into the customized micro-devices for in-situ Lorentz transmission electron microscopy observations, we implement these three operations of skyrmions using nanosecond current pulses with a low a current density about $10^{10}$ A/m$^2$ at room temperature. A notched structure can create or delete magnetic skyrmions depending on the direction and magnitude of current pulses. We further show that the magnetic skyrmions can be deterministically shifted step-by-step by current pulses, allowing the establishment of the universal current-velocity relationship. These experimental results have immediate significance towards the skyrmion-based memory or logic devices., 16 pages

Flexible magnetic materials with robust and controllable perpendicular magnetic anisotropy (PMA) are highly desirable for developing flexible high-performance spintronic devices. However, it is still challenge to fabricate PMA films on polymers directly. Here, we report a facile method for synthesizing single-crystal freestanding SrRuO3 membranes with controlled crystal structure and orientation using water-soluble Ca3-xSrxAl2O6 sacrificial layers. Through cooperative effect of crystal structure and orientation, flexible membranes reveal highly tunable magnetic anisotropy from in-plane to out-of-plane with a remarkable PMA energy of 7 × 106 erg·cm−3. First-principle calculations reveal that the underlying mechanism of PMA modulation is intimately correlated with structure-controlled Ru 4d-orbital occupation, as well as spin-orbital matrix element differences, dependent on the crystal orientation. In addition, even after 10,000 bending cycles, the PMA keeps stable, indicating a robust magnetism reliability in the prepared films. This work provides a feasible approach to prepare the flexible oxide films with strong and controllable PMA.

With the continuous progress of materials science and biology, the significance of biomaterials with dual characteristics of materials science and biology is keeping on increasing. Nowadays, more and more biomaterials are being used in tissue engineering, pharmaceutical engineering and regenerative medicine. In repairing bone defects caused by trauma, tumor invasion, congenital malformation and other factors, a variety of biomaterials have emerged with different characteristics, such as surface charge, surface wettability, surface composition, immune regulation and so on, leading to significant differences in repair effects. This paper mainly discusses the influence of surface charge of biomaterials on bone formation and the methods of introducing surface charge, aiming to promote bone formation by changing the charge distribution on the surface of the biomaterials to serve the clinical treatment better.随着材料学、生物学领域研究的不断进步，集合材料学和生物学双重特性的生物材料的重要性日益凸显。目前生物材料在组织工程、制药工程和再生医学等领域应用较为广泛。在因外伤、肿瘤侵袭、先天畸形等因素造成的骨缺损修复领域，已涌现出很多不同的生物材料，它们在表面电荷、表面润湿性、表面成分、免疫调节等方面各自具有不同的特性，导致修复效果各具差异。本文就生物材料表面电荷对骨形成的影响，以及在生物材料表面引入电荷的方法展开论述，为生物材料表面电荷分布促进骨形成奠定理论基础，以期今后更好地服务于临床研究。.

Oxygen octahedral tilting has been recognized to strongly interact with spin, charge, orbital, and lattice degrees of freedom in perovskite oxides. Here, we observe a strain‐driven stripe‐like morphology of two supertetragonal (monoclinic Cc and Cm) phases in the strained BiFeO3/LaAlO3 thin films. The two supertetragonal phases have a similar giant axial ratio but differences in oxygen pyramid tilting mode. Especially, the competition between polar instability and oxygen pyramid tilting is identified using atomically resolved scanning transmission electron microscopy, leading to the polarization rotation across the phase boundary. In addition, microtwins are observed in the Cc phase. Our findings provide new insights of the coupling between ferroelectric polarization and oxygen pyramid tilting in oxide thin films and will help to design novel phase morphology with desirable ferroelectric polarization and properties for new applications in perovskite oxides.

The electrocaloric effect in ferroelectric materials has drawn much attention due to its potential applications in integrated circuit cooling and novel cooling devices. In contrast to the widely researched positive electrocaloric effect, the negative electrocaloric effect has received much less attention due to the lack of any effective methods for significant enhancement. In this work, we fabricated PbZrO3 thin film on a Pt/Si substrate by the sol-gel method. By controlling the interface conditions between the thin film and substrate, we induced defects into the interface and stabilized a transient ferroelectric phase in the PbZrO3 thin film. The emergence of the transient ferroelectric phase postpones the antiferroelectric-ferroelectric phase transition. As a result, a negative electrocaloric effect up to -18.5 K is estimated near room temperature, the highest one ever reported in this temperature range. This result suggests a new strategy to enhance the negative electrocaloric effect and may benefit the application of PbZrO3 thin films in cooling devices.

Modern Cs-corrected high-resolution transmission electron microscopy (HRTEM) has pushed the resolution limit to sub-angstrom scale and has made possible the quantitative analyses of local aperiodic atomic structures. After images have been obtained, a Wiener filter is often used to improve the signal-to-noise ratio, especially for those samples containing both crystal and large amorphous components. However, a Wiener filter may introduce distortions in the original experimental images. From this point of view, having a fundamental understanding of the effect of a Wiener filter on the accuracy of atomic displacement measurements in aperiodic structures is important. In this work, we first review the principle of the Wiener filter and theoretically discuss the origin of the distortions induced in aperiodic structures by using a Wiener filter. Then, using hypothetical experimental systems that contains both aperiodic crystal structures and amorphous layers, we carried out synthetic experiments to quantitatively estimate the effect of the Wiener filter on the measurements of aperiodic displacements. Compared with the values for a non-filtered image, the signal-to-noise ratio was significantly improved, and the accuracy of the displacement measurement was not decreased when proper Wiener filter parameters were used. Such results are of great importance for the processing of HRTEM images.

Magnetic measurement by transmitted electrons at nanometer or even atomic scale is always an attractive and challenging issue in the transmission electron microscope. Electron magnetic circular dichroism, proposed in 2003 and realized in 2006, opens a new insight into the measurement of local magnetic properties. Later, it is developed into a powerful technique for quantitative magnetic measurement with site specificity and element specificity at high spatial resolution over years of efforts, both in the aspect of theory and experiments. The novel technique has been widely applied to the characterization of magnetic materials now. This present review gives an overview of its development and applications in the past fifteen years since its invention. The theory of electron magnetic circular dichroism and its development are reviewed. The diffraction geometry and experimental setups are summarized. The general way for quantitative measurement of magnetic parameters is presented with typical cases. Representative breakthroughs in method development and applications over a wide range of materials are then described. Finally, prospects for future development are briefly discussed.

Efficient photocatalysis is important for sustainable energy. Recently, an unconventional photocatalyst based on intrinsic plasmon, called intrinsic plasmonic photocatalyst (IPP), seems promising for higher efficiency in hydrogen evolution. This catalyst seems to benefit from the advantages of visible light absorption, plasmon-assisted hot carrier generation, and good catalytic stability over conventional semiconductor photocatalysts. In this work, we report the relative hydrogen evolution efficiency under visible light irradiation of a family of IPP based on alkaline earth niobates (MNbO3, where M = Ca, Sr, or Ba), with efficiency of CaNbO3 > SrNbO3 > BaNbO3. The contributions of electron–phonon coupling time constant and solar energy absorption to the hydrogen evolution efficiency are identified as key based on our comprehensive study and characterization of carrier density (1022 cm–3), plasmon absorption, carrier dynamics, and surface area. This study demonstrates a generic approach to create a family of IPPs and further validates the role of solar energy absorption by intrinsic plasmon resonance in the enhancement of photocatalytic efficiency. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version The NUS researchers acknowledge Singapore National Research Foundation under its Competitive Research Funding ’Oxide Electronics on silicon beyond Moore’ (NRF-CRP15-2015-01). X.R.W. acknowledges the support from the Nanyang Assistant Professorship grant from Nanyang Technological University, Academic Research Fund Tier 1 (RG108/17 and RG177/18) from Singapore Ministry of Education. P.Y. is supported by SSLS via NUS Core Support (C-380-003-003-001). The authors thank the Singapore Synchrotron Light Source (SSLS) for providing the facility necessary for conducting the research. The laboratory is a National Research Infrastructure under the National Research Foundation (NRF) Singapore. The authors also thank for the support from Dr. Zhongxin Chen for the photocatalytic reaction measurements. The computational work for this article was partially performed on resources of the National Supercomputing Centre, Singapore (https://www.nscc.sg).

The adsorption of water molecules on tricalcium silicate (C3S), which influences the initial hydration of C3S, is still unclear at the atomistic level. In the present paper, density functional theory is employed to depict the adsorption of a single water molecule on seven low-index M3-C3S surfaces. The calculations show that both molecular and dissociative adsorption can occur on the C3S surfaces and that the latter mode is preferential. All of the ionic O atoms on the C3S surfaces can adsorb the H atoms from dissociated water molecules, while only two-coordinated covalent O atoms on the surfaces can form O H chemical bonds. The electronic structures of the ionic and two-coordinated covalent O atoms in the first atomic layer of the C3S surfaces show similar charge density localization of the valence band maximum (VBM), which can describe the variations in the reactivity of the ionic O atoms in the bulk or exposed on the surface slab. The partial density of states (PDOS) analysis shows that the formation of new Ca O bonds is mainly due to the overlap of O-2s and Ca-3p orbitals and O-2p and Ca-3d orbitals. Furthermore, the position of the OH group generated from the dissociated water molecule is found to significantly affect the adsorption energy. The general order of the adsorption energy in terms of the position of the OH group is Ehollow > Ebridge > Etop. The findings in this study provide additional support for the fundamental understanding of C3S hydration.

Bismuth and rare earth elements have been identified as effective substituent elements in the iron garnet structure, allowing an enhancement in magneto-optical response by several orders of magnitude in the visible and near-infrared region. Various mechanisms have been proposed to account for such enhancement, but testing of these ideas is hampered by a lack of suitable experimental data, where information is required not only regarding the lattice sites where substituent atoms are located but also how these atoms affect various order parameters. Here, we show for a Bi-substituted lutetium iron garnet how a suite of advanced electron microscopy techniques, combined with theoretical calculations, can be used to determine the interactions between a range of quantum-order parameters, including lattice, charge, spin, orbital, and crystal field splitting energy. In particular, we determine how the Bi distribution results in lattice distortions that are coupled with changes in electronic structure at certain lattice sites. These results reveal that these lattice distortions result in a decrease in the crystal-field splitting energies at Fe sites and in a lifted orbital degeneracy at octahedral sites, while the antiferromagnetic spin order remains preserved, thereby contributing to enhanced magneto-optical response in bismuth-substituted iron garnet. The combination of subangstrom imaging techniques and atomic-scale spectroscopy opens up possibilities for revealing insights into hidden coupling effects between multiple quantum-order parameters, thereby further guiding research and development for a wide range of complex functional materials.

Here we have developed an approach of three-dimensional (3D) measurement of magnetic moment vectors in three Cartesian directions using electron magnetic chiral dichroism (EMCD) at atomic scale. Utilizing a subangstrom convergent electron beam in the scanning transmission electron microscopy (STEM), beam-position-dependent chiral electron energy-loss spectra (EELS), carrying the EMCD signals referring to magnetization in three Cartesian directions, can be obtained during the scanning across the atomic planes. The atomic resolution EMCD signals from all of three directions can be separately obtained simply by moving the EELS detector. Moreover, the EMCD signals can be remarkably enhanced using a defocused electron beam, relieving the issues of low signal intensity and signal-to-noise-ratio especially at atomic resolution. Our proposed method is compatible with the setup of the widely used atomic resolution STEM-EELS technique and provides a straightforward way to achieve 3D magnetic measurement at atomic scale on newly developing magnetic-field-free TEM.

Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a promising candidate as solid electrolyte and Li+ conductive component in the composite electrodes of all-solid-state Li-ion batteries. For both applications, reducing the sintering temperature of LATP while preserving its electrochemical properties is highly desired. This work is dedicated to reducing the sintering temperature of LATP from conventionally around 1000 °C to a low temperature of 775 °C with adding an extra 10 wt % of Li2CO3 to the precursors by a reactive sintering process. Comparative investigations with the stoichiometric LATP prepared by the same sintering method indicate that the combination effect of reactive sintering and Li2CO3-excess promotes the liquid phase sintering within LATP yielding a high relative density of 95.3%, whereas the stoichiometric LATP can only achieve a comparable relative density at 875 °C. Furthermore, the reactive sintering assisted Li2CO3-excess LATP exhibits a significantly higher ionic conductivity of 0.65 mS cm−1 at 25 °C and lower total activation energy of 0.334 eV compared with that of the stoichiometric LATP. Correlative studies on the microstructure and the separated specific grain/grain boundary conductivities for the two samples reveal that the improvement of Li+ conductivity for Li-excess LATP is attributed to its smaller total grain boundary thickness.

Two-dimensional (2D) van der Waals magnets have drawn considerable attention in recent years triggered by the huge interest in novel magnetism and spintronic devices. Magnetic measurement of 2D van der Waals (vdW) magnets is crucial to understand the physical origin of magnetism in 2D limits. Therefore, advanced magnetic characterization techniques are highly required. However, only a limited number of such techniques are available due to the extremely small volume of 2D vdW magnets. Here, we introduce the electron magnetic chiral dichroism (EMCD) technique in transmission electron microscope (TEM) to measure 2D vdW crystals. In comparison with some other already-employed techniques in 2D magnets, EMCD is able to quantitatively measure magnetic parameters in three orthogonal directions at nanometer or even at atomic scale. We then perform EMCD simulations on several typical 2D vdW magnets with respect to the accelerating voltage, the number of atomic layers and beam tilt under zone axial orientation. The intensity and distribution of EMCD signals in three orthogonal directions are given in the diffraction plane, thereby providing an optimized design to achieve EMCD measurements. Finally, we discuss the signal-to-noise-ratio and required electron dose in order to obtain a measurable EMCD signal for 2D vdW magnets. Our results provide a feasibility analysis and guideline to measure 2D vdW magnets in future experiments.

The hierarchical microstructures of high-entropy alloys (HEAs) can result in highly complex magnetic textures and properties. Here, we use high spatial resolution correlative magnetic, structural and chemical imaging to investigate magnetic textures in phase separated AlCoxCr1 – xFeNi (x = 0.5 and 1) HEAs. The AlCoFeNi HEA, which contains nm-sized A2 precipitates in a B2 matrix, supports large magnetic domains with small-angle magnetization variations. In contrast, the AlCo(Cr)FeNi HEA, which undergoes hierarchical phase separation, contains an unexpected distribution of magnetic vortices within individual A2 precipitates in a weakly ferromagnetic B2 host, in addition to weakly ferromagnetic or nonmagnetic B2 precipitates in large magnetic domains of the A2 phase, as well as Fe-Co-rich inter-phase A2 regions that have strong magnetization. The coercivity is attributed to a complicated magnetization reversal process, which includes the successive reversal of the magnetic vortices. These results provide important insight for the rational design of HEAs with unique and tailored magnetic properties.

Grain boundaries could exhibit exceptional electronic structure and exotic properties, which are determined by a local atomic configuration and stoichiometry that differs from the bulk. However, optical and plasmonic properties at the grain boundaries in metallic oxides have rarely been discussed before. Here, we show that non-stoichiometric grain boundaries in the newly discovered metallic SrNbO

Electrical control of material properties based on ionic liquids (IL) has seen great development and emerging applications in the field of functional oxides, mainly understood by the electrostatic and electrochemical gating mechanisms. Compared to the fast, flexible, and reproducible electrostatic gating, electrochemical gating is less controllable owing to the complex behaviors of ion migration. Here, the interface‐dependent oxygen migration by electrochemical gating is resolved at the atomic scale in the LaAlO3–SrTiO3 system through ex situ IL gating experiments and on‐site atomic‐resolution characterization. The difference between interface structures leads to the controllable electrochemical oxygen migration by filling oxygen vacancies. The findings not only provide an atomic‐scale insight into the origin of interface‐dependent electrochemical gating but also demonstrate an effective way of engineering interface structure to control the electrochemical gating., The interface‐dependent oxygen migration by electrochemical gating is resolved at the atomic scale in the LaAlO3–SrTiO3 system through ex situ ionic liquid gating experiments and on‐site atomic‐resolution characterization. The difference between interface structures leads to the controllable electrochemical oxygen migration by filling oxygen vacancies.

Aberration-corrected scanning transmission electron microscopy (STEM) provides real space imaging and spectroscopy at atomic resolution with a new level of sensitivity to structure, bonding, elemental valence and even dynamics. It has developed into the most powerful characterization and even fabrication platform for all materials, especially for functional materials with complex structural features that dynamically respond to external fields. Several representative examples of functional materials are shown, including piezoelectric and photoelectric materials, functional oxide interfaces, metal–organic framework (MOF)-derived transition metal oxide/phosphide catalysts and two-dimensional (2D) materials. In piezoelectric systems, atomic-resolution polarization mapping by Z-contrast imaging shows the intimate coexistence of two ferroelectric phases inside nanodomains. Quantitative STEM imaging and EELS spectroscopy reveal the underlying mechanism of the exotic coupling between polarization and charge at a functional oxide interface. Under the low-voltage STEM, defects in 2D materials are clearly visible, for example novel edges and single atom dopants. The dynamic behavior of single atoms in vacancies of monolayer MoS2 is shown to highlight the electron-beam induced nanofabrication ability of aberration-corrected STEM. Thanks to the rapid development of segmented/pixelated detectors, differential phase contrast and 4D STEM techniques are promising for the near future, providing more opportunities to understand the link between structure and functionality.

The present work demonstrates ferroelectric to antiferroelectric transition aided electric field control of positive and negative electrocaloric effects (ECE). In this context, epitaxial PbZrO3 (PZO) thin films were grown on (111) Nb:SrTiO3 single crystal substrates by the sol–gel method, and the epitaxial growth was confirmed by atomic resolution scanning transmission electron microscopy (STEM) high angle annular dark field (HAADF) images. The structural and elemental analysis revealed a gradual increase of natural lead volatilization from the middle to the top in PZO thin films. The electrocaloric effect (ECE) was calculated using Maxwell equations corresponding to 10 kHz and 100 Hz P–E data and was found to be −10.5 K (negative ECE) at 375 K and 30 K (positive ECE) at 300 K. Intriguingly, both negative and positive ECE were found in the same phase transition sequence, that is, from an antiferroelectric phase to a ferroelectric phase. The frequency dependence of ECE is found to be dependent on the polarization switching dynamics and kinetics. These results are not only scientifically important for providing an easy way to combine the negative and positive ECE together to further enhance the cooling efficiency but are also technically important for future ECE devices.