Large Manipulation of Ferrimagnetic Curie Temperature by A-Site Chemical Substitution in ACuFeReO (A = Na, Ca, and La) Half Metals.

CaCuFeReO and LaCuFeReO quadruple perovskite oxides are well known for their high ferrimagnetic Curie temperatures and half-metallic electronic structures. By A-site chemical substitution with lower valence state Na, an isostructural compound NaCuFeReO with both A- and B-site ordered quadruple perovskite structures in -3 symmetry was prepared using high-pressure and high-temperature techniques. The X-ray absorption study demonstrates the valence states to be Cu, Fe, and Re.

In Situ Self-Assembled 200 nm-Depth Highly Active Layer Non-Precious Metals Catalyst for Industrial Water Electrolysis.

Nickel-based electrocatalysts are promising for industrial water electrolysis, but the dense hydroxyl oxide layer formed during the oxygen evolution reaction (OER) limits active sites accessibility and presents challenges in balancing structural stability with effective charge transfer. Based on this, an efficient in situ leaching strategy is proposed to construct grain boundary-rich catalyst structure with high charge transfer ability and a deep catalytic active layer reached >200-nm. Under OER conditions, stable sub-nano NiAl particles are embedded in Ni(Fe)OOH, originating from leaching out the unstable NiAl phase of the initial NiAl/NiAl alloy doped with Fe.

Enhancing Reversibility and Kinetics of Anionic Redox in O3-NaLiMnO through Controlled P2 Intergrowth.

Anionic redox chemistry can surpass theoretical limits of conventional layered oxide cathodes in energy density. A recent model system of sodium-ion batteries, O3-NaLiMnO, demonstrated full anionic redox capacity but is limited in reversibility and kinetics due to irreversible structural rearrangement and oxygen loss. Solutions to these issues are missing due to the challenging synthesis.

Suppressing Structure Delamination for Enhanced Electrochemical Performance of Solid Oxide Cells.

Reversible solid oxide cells (rSOCs) have significant potential as efficient energy conversion and storage systems. Nevertheless, the practical application of their conventional air electrodes, such as LaSrMnO (LSM), BaSrCoFeO (BSCF), and PrBaCaCoO (PBCC), remains unsatisfactory due to interface delamination during prolonged electrochemical operation. Using micro-focusing X-ray absorption spectroscopy (µ-XAS), a decrease (increase) in the co-valence state from the electrode surface to the electrode/electrolyte interface is observed, leading to the above delamination.

Enhanced polarization switching characteristics of HfO ultrathin films via acceptor-donor co-doping.

In the realm of ferroelectric memories, HfO-based ferroelectrics stand out because of their exceptional CMOS compatibility and scalability. Nevertheless, their switchable polarization and switching speed are not on par with those of perovskite ferroelectrics. It is widely acknowledged that defects play a crucial role in stabilizing the metastable polar phase of HfO.

Three-dimensional ultrafast charge-density-wave dynamics in CuTe.

Charge density waves (CDWs) involved with electronic and phononic subsystems simultaneously are a common quantum state in solid-state physics, especially in low-dimensional materials. However, CDW phase dynamics in various dimensions are yet to be studied, and their phase transition mechanism is currently moot. Here we show that using the distinct temperature evolution of orientation-dependent ultrafast electron and phonon dynamics, different dimensional CDW phases are verified in CuTe.

High-Pressure Synthesis of Quadruple Perovskite Oxide CaCuCrReO with a High Ferrimagnetic Curie Temperature.

An AA'BB'O-type quadruple perovskite oxide of CaCuCrReO was synthesized at 18 GPa and 1373 K. Both an A- and B-site ordered quadruple perovskite crystal structure was observed, with the space group -3. The valence states are verified to be CaCuCrReO by bond valence sum calculations and synchrotron X-ray absorption spectroscopy.

Spin polarized Fe-Ti pairs for highly efficient electroreduction nitrate to ammonia.

Electrochemical nitrate reduction to ammonia offers an attractive solution to environmental sustainability and clean energy production but suffers from the sluggish *NO hydrogenation with the spin-state transitions. Herein, we report that the manipulation of oxygen vacancies can contrive spin-polarized Fe-Ti pairs on monolithic titanium electrode that exhibits an attractive NH yield rate of 272,000 μg h mg and a high NH Faradic efficiency of 95.2% at -0.

Enhanced Exchange Bias in Epitaxial High-Entropy Oxide Heterostructures.

High-entropy oxides (HEOs) have gained significant interest in recent years due to their unique structural characteristics and potential to tailor functional properties. However, the electronic structure of the HEOs currently remains vastly unknown. In this work, combining magnetometry measurements, scanning transmission electron microscopy, and element-specific X-ray absorption spectroscopy, the electronic structure and magnetic properties of the perovskite-HEO La(CrMnFeCoNi)O epitaxial thin films are systemically studied.

Antiferroelectricity-Induced Negative Thermal Expansion in Double Perovskite Pb CoMoO.

Materials with negative thermal expansion (NTE) attract significant research attention owing to their unique physical properties and promising applications. Although ferroelectric phase transitions leading to NTE are widely investigated, information on antiferroelectricity-induced NTE remains limited. In this study, single-crystal and polycrystalline Pb CoMoO samples are prepared at high pressure and temperature conditions.

Spin State Disproportionation in Insulating Ferromagnetic LaCoO Epitaxial Thin Films.

The origin of insulating ferromagnetism in epitaxial LaCoO films under tensile strain remains elusive despite extensive research efforts are devoted. Surprisingly, the spin state of its Co ions, the main parameter of its ferromagnetism, is still to be determined. Here, the spin state in epitaxial LaCoO thin films is systematically investigated to clarify the mechanism of strain-induced ferromagnetism using element-specific X-ray absorption spectroscopy and dichroism.

Insights into Reversible Sodium Intercalation in a Novel Sodium-Deficient NASICON-Type Structure:Na □ Co Fe V(PO ).

The rational design of novel high-performance cathode materials for sodium-ion batteries is a challenge for the development of the renewable energy sector. Here, a new sodium-deficient NASICON phosphate, namely Na □ Co Fe V(PO ) , demonstrating the excellent electrochemical performance is reported. The presence of Co allows a third Na to participate in the reaction thus exhibiting a high reversible capacity of ≈155 mAh g in the voltage range of 2.

Origin of the Seriously Limited Anionic Redox Reaction of Li-Rich Cathodes in Sulfide All-Solid-State Batteries.

Li-rich layered oxide (LLO) cathode materials with mixed cationic and anionic redox reactions display much higher specific capacity than other traditional layered oxide materials. However, the practical specific capacity of LLO during the first cycle in sulfide all-solid-state lithium-ion batteries (ASSLBs) is extremely low. Herein, the capacity contribution of each redox reaction in LLO during the first charging process is qualitatively and quantitatively analyzed by comprehensive electrochemical and structural measurements.

Unusual double ligand holes as catalytic active sites in LiNiO.

Designing efficient catalyst for the oxygen evolution reaction (OER) is of importance for energy conversion devices. The anionic redox allows formation of O-O bonds and offers higher OER activity than the conventional metal sites. Here, we successfully prepare LiNiO with a dominant 3dL configuration (L is a hole at O 2p) under high oxygen pressure, and achieve a double ligand holes 3dL under OER since one electron removal occurs at O 2p orbitals for Ni oxides.

Mo-Incorporated Magnetite Fe O Featuring Cationic Vacancies Enabling Fast Lithium Intercalation for Batteries.

Transition metal oxides (TMOs) as high-capacity electrodes have several drawbacks owing to their inherent poor electronic conductivity and structural instability during the multi-electron conversion reaction process. In this study, the authors use an intrinsic high-valent cation substitution approach to stabilize cation-deficient magnetite (Fe O ) and overcome the abovementioned issues. Herein, 5 at% of Mo -ions are incorporated into the spinel structure to substitute octahedral Fe -ions, featuring ≈1.

Twisted oxide lateral homostructures with conjunction tunability.

Epitaxial growth is of significant importance over the past decades, given it has been the key process of modern technology for delivering high-quality thin films. For conventional heteroepitaxy, the selection of proper single crystal substrates not only facilitates the integration of different materials but also fulfills interface and strain engineering upon a wide spectrum of functionalities. Nevertheless, the lattice structure, regularity and crystalline orientation are determined once a specific substrate is chosen.

Photonic-Crafting of Non-Volatile and Rewritable Antiferromagnetic Spin Textures with Drastic Difference in Electrical Conductivity.

Antiferromagnetic spintronics is an emerging field of non-volatile data storage and information processing. The zero net magnetization and zero stray fields of antiferromagnetic materials eliminate interference between neighbor units, leading to high-density memory integrations. However, this invisible magnetic character at the same time also poses a great challenge in controlling and detecting magnetic states in antiferromagnets.

Presence of Delocalized Ti 3d Electrons in Ultrathin Single-Crystal SrTiO.

Strontium titanate (STO), with a wide spectrum of emergent properties such as ferroelectricity and superconductivity, has received significant attention in the community of strongly correlated materials. In the strain-free STO film grown on the SrRuO buffer layer, the existing polar nanoregions can facilitate room-temperature ferroelectricity when the STO film thickness approaches 10 nm. Here we show that around this thickness scale, the freestanding STO films without the influence of a substrate show the tetragonal structure at room temperature, contrasting with the cubic structure seen in bulk form.

Extremely Fast Optical and Nonvolatile Control of Mixed-Phase Multiferroic BiFeO via Instantaneous Strain Perturbation.

Multiferroics-materials that exhibit coupled ferroic orders-are considered to be one of the most promising candidate material systems for next-generation spintronics, memory, low-power nanoelectronics and so on. To advance potential applications, approaches that lead to persistent and extremely fast functional property changes are in demand. Herein, it is revealed that the phase transition and the correlated ferroic orders in multiferroic BiFeO (BFO) can be modulated via illumination of single short/ultrashort light pulses.

Mechanically tunable exchange coupling of Co/CoO bilayers on flexible muscovite substrates.

The employment of flexible muscovite substrates has given us the feasibility of applying strain to heterostructures dynamically by mechanical bending. In this study, this novel approach is utilized to investigate strain effects on the exchange coupling in ferromagnetic Co and anti-ferromagnetic CoO (Co/CoO) bilayers. Two different Co/CoO bilayer heterostructures were grown on muscovite substrates by oxide molecular beam epitaxy, with the CoO layer being purely (111)- and (100)-oriented.

Deterministic optical control of room temperature multiferroicity in BiFeO thin films.

Controlling ferroic orders (ferroelectricity, ferromagnetism and ferroelasticity) by optical methods is a significant challenge due to the large mismatch in energy scales between the order parameter coupling strengths and the incident photons. Here, we demonstrate an approach to manipulate multiple ferroic orders in an epitaxial mixed-phase BiFeO thin film at ambient temperature via laser illumination. Phase-field simulations indicate that a light-driven flexoelectric effect allows the targeted formation of ordered domains.

Development of a long trace profiler in situ at National Synchrotron Radiation Research Center.

To achieve an ultrahigh resolution of a beamline for soft X-rays at the Taiwan Photon Source (TPS), the profile of a highly precise grating is required at various curvatures. The slope error could be decreased to 0.1 µrad (rms) at a thermal load with a specially designed bender having 25 actuators.