Spin–orbit torque (SOT) induced magnetization switching in an energy-efficient and fast way has exhibited great application potential in next generation magnetic memories. However, a complicated layer structure is usually needed to break the mirror symmetry for achieving SOT induced field-free magnetization switching. Here, we report a sizeable field-free magnetization switching through large out-of-plane SOT in the chemically disordered A1-CoxPt100−x single layers within a Co composition range from 40 to 70. The largest absolute out-of-plane SOT efficiency is found at its equiatomic concentration (Co50Pt50), in which the absolute in-plane SOT efficiency also reaches the maximum value, 22.7 Oe/107 A cm−2. We further demonstrate that the symmetry dependence of field-free magnetization switching might arise from the chemically ordered L11-CoPt nano-scaled platelets formed during the sample deposition. We expect that the experimental identification of the field-free magnetization switching in the ferromagnetic CoPt single layer is desirable to simplify the applications of spin logic devices.

The solid electrolyte interphase (SEI) plays a crucial role in extending the life of aqueous batteries. The traditional anion-derived SEI formation in aqueous electrolytes highly depends on high-concentrated organic fluorinating salts, resulting in low forming efficiency and long-term consumption. In response, this study proposes a bifunctional fluorocarbon electrode additive (BFEA) that enables electrochemical pre-reduction instead of TFSI anion to form the LiF-rich SEI and in situ produce conductive graphite inside the anode before the lithiation. The BFEA lowers the salt dependence of aqueous electrolytes, enabling the inorganic LiCl electrolyte to work first, but also successfully achieves a high SEI formation efficiency in the relatively low 10 m LiTFSI without mass transfer concerns, suppressing the parasitic hydrogen evolution from 11.24 to 4.35 nmol min-1. Besides, BFEA strengthens the intrinsic superiority of Li storage reaction by lowering battery polarization resulting from the in situ production of graphite, promoting charge transfer of electrode kinetics. Compared with the control group, the demonstrated Ah-level pouch cell employing BFEA exhibits better cycle stability above 300 cycles with higher capacity retention of 78.2% and the lower decay of the round-trip efficiency (△RTE = 2%), benefiting for maintaining the high efficiency and reducing heat accumulation in large-scale electric energy storage.

Li-ion batteries employing stoichiometric layered Li metal oxides as cathodes are now reaching the energy density limits due to single cationic redox chemistry. Lattice oxygen redox (LOR) has been discovered in these materials, as a high-energy-density paradigm observed in Li-rich materials. Nevertheless, the origin of this process is not understood, preventing the rational design of better cathode materials. Here, employing stoichiometric Ni-based cathodes, it is demonstrated that LOR originates from a dynamic transition metal (TM) network caused by ion migration during the electrochemical process. This network is confirmed to be ribbon through both ex- and in-situ STEM observations, facilitating reversible LOR. Finally, a t2g orbital population rule is proposed to guide the design of ordered TM networks, supported by calculated structures and the synthesized ordered TM oxides reported. This work explains the mechanism of LOR in stoichiometric layered cathode materials, and sets a promising direction for the design of high-energy-density cathodes through the regulation of TM ordering.

AbstractAluminum current collectors are widely used in nonaqueous batteries owing to their cost-effectiveness, lightweightness, and ease of fabrication. However, they are excluded from aqueous batteries due to their severe corrosion in aqueous solutions. Here, we propose hydrolyzation-type anodic additives to form a robust passivation layer to suppress corrosion. These additives dramatically lower the corrosion current density of aluminum by nearly three orders of magnitude to ~10−6 A cm−2. In addition, realizing that electrochemical corrosion accompanies anode prelithiation, we propose a prototype of self-prolonging aqueous Li-ion batteries (Al ||LiMn2O4 ||TiO2), whose capacity retention rises from 49.5% to 70.1% after 200 cycles. A sacrificial aluminum electrode where electrochemical corrosion is utilized is introduced as an electron supplement to prolong the cycling life of aqueous batteries. Our work addresses the short-life issue of aqueous batteries resulting from the corrosion of the current collector and lithium loss from side reactions.

The aggravated mechanical and structural degradation of layered oxide cathode materials upon high-voltage charging invariably causes fast capacity fading, but the underlying degradation mechanisms remain elusive. Here we report a new type of mechanical degradation through the formation of a kink band in a Mg and Ti co-doped LiCoO2 cathode charged to 4.55 V (vs Li/Li+). The local stress accommodated by the kink band can impede crack propagation, improving the structural integrity in a highly delithiated state. Additionally, machine-learning-aided atomic-resolution imaging reveals that the formation of kink bands is often accompanied by the transformation from the O3 to O1 phase, which is energetically favorable as demonstrated by first-principles calculations. Our results provide new insights into the mechanical degradation mechanism of high-voltage LiCoO2 and the coupling between electrochemically triggered mechanical failures and structural transition, which may provide valuable guidance for enhancing the electrochemical performance of high-voltage layered oxide cathode materials for lithium-ion batteries.

Identifying a suitable water-soluble sacrificial layer is crucial to fabricating large-scale freestanding oxide membranes, which offer attractive functionalities and integrations with advanced semiconductor technologies. Here, we introduce a water-soluble sacrificial layer, "super-tetragonal" Sr4Al2O7 (SAOT). The low-symmetric crystal structure enables a superior capability to sustain epitaxial strain, allowing for broad tunability in lattice constants. The resultant structural coherency and defect-free interface in perovskite ABO3/SAOT heterostructures effectively restrain crack formation during the water release of freestanding oxide membranes. For a variety of nonferroelectric oxide membranes, the crack-free areas can span up to a millimeter in scale. This compelling feature, combined with the inherent high water solubility, makes SAOT a versatile and feasible sacrificial layer for producing high-quality freestanding oxide membranes, thereby boosting their potential for innovative device applications.

Recent progress on the signatures of pressure-induced high temperature superconductivity in Ruddlesden Popper (RP) nickelates (Lan+1NinO3n+1) has attracted growing interest in both theoretical calculations and experimental efforts. The fabrication of high-quality single crystalline RP nickelate thin films is critical for possible reducing the superconducting transition pressure and advancing applications in microelectronics in the future. In this study, we report the observations of an active phase transition in RP nickelate films induced by misfit strain. We found that RP nickelate films favor the perovskite structure (n = infinite) under tensile strains, while compressive strains stabilize the La3Ni2O7 (n = 2) phase. The selection of distinct phases is governed by the strain dependent formation energy and electronic configuration. In compressively strained La3Ni2O7, we experimentally determined splitting energy is ~0.2 eV and electrons prefer to occupy in-plane orbitals. First principles calculations unveil a robust coupling between strain effects and the valence state of Ni ions in RP nickelates, suggesting a dual driving force for the inevitable phase co-existence transition in RP nickelates. Our work underscores the sensitivity of RP nickelate formation to epitaxial strain, presenting a significant challenge in fabricating pure-phase RP nickelate films. Therefore, special attention to stacking defects and grain boundaries between different RP phases is essential when discussing the pressure-induced superconductivity in RP nickelates.

Hybrid devices that combine superconductors (S) and semiconductors (Sm) have attracted great attention due to the integration of the properties of both materials, which relies on the interface details and the resulting coupling strength and wavefunction hybridization. However, until now, none of the experiments have reported good control of the band alignment of the interface, as well as its tunability to the coupling and hybridization. Here, the interface is modified by inducing specific argon milling while maintaining its high quality, e.g., atomic connection, which results in a large induced superconducting gap and ballistic transport. By comparing with Schrödinger-Poisson calculations, it is proven that this method can vary the band bending/coupling strength and the electronic spatial distribution. In the strong coupling regime, the coexistence and tunability of crossed Andreev reflection and elastic co-tunneling-key ingredients for the Kitaev chain-are confirmed. This method is also generic for other materials and achieves a hard and huge superconducting gap in lead and indium antimonide nanowire (Pb-InSb) devices. Such a versatile method, compatible with the standard fabrication process and accompanied by the well-controlled modification of the interface, will definitely boost the creation of more sophisticated hybrid devices for exploring physics in solid-state systems.

The deposition of volatilized Na + on the surface of the cathode during sintering results in the formation of surface residual alkali (NaOH/Na 2 CO 3 NaHCO 3 ) in layered cathode materials, leading to serious interfacial reactions and performance degradation. This phenomenon is particularly evident in O3‐NaNi 0.4 Cu 0.1 Mn 0.4 Ti 0.1 O 2 (NCMT). In this study, a strategy is proposed to transform waste into treasure by converting residual alkali into a solid electrolyte. Mg(CH 3 COO) 2 and H 3 PO 4 are reacted with surface residual alkali to generate the solid electrolyte NaMgPO 4 on the surface of NCMT, which can be labeled as NaMgPO4@NaNi 0.4 Cu 0.1 Mn 0.4 Ti 0.1 O 2 ‐ X (NMP@NCMT‐ X , where X indicates the different amounts of Mg 2+ and PO 4 3− ). NaMgPO 4 acts as a special ionic conductivity channel on the surface to improve the kinetics of the electrode reactions, remarkably improving the rate capability of the modified cathode at a high current density in the half‐cell. Additionally, NMP@NCMT‐2 enables a reversible phase transition from the P3 to OP2 phase in the charge–discharge process above 4.2 V and achieves a high specific capacity of 157.3 mAh g −1 and outstanding capacity retention in the full cell. The strategy can effectively and reliably stabilize the interface and improve the performance of layered cathodes for Na‐ion batteries (NIBs).

High-quality single-crystalline hexagonal Ruthenium thin films were epitaxially grown on (110)-oriented LaAlO3 substrates. The hexagonal Ruthenium is found to be a semimetal demonstrating nonsaturating and near-quadratic field-dependent magnetoresistance (MR). Remarkably, while exhibiting a linear Hall effect at temperatures above 50 K, the Hall resistivity of hexagonal Ruthenium undergoes an unexpectedly sign reversal at magnetic field strengths exceeding 10 T, specifically within the low-temperatures range of 2-30 K. First-principles calculations well reproduce these characteristics, including both the nonsaturating MR and the sign-reversal Hall effect. Based on the two-band model and semiclassical equation of motion, we found a general principle that at low temperatures or in high fields, the sign of Hall effect is governed by charge carriers with higher density, whereas at higher temperatures or in lower fields, it is dominated by carriers with higher mobility. Consequently, materials where higher-density charge carriers possess lower mobility are expected to exhibit a sign reversal in Hall resistivity. This framework offers fresh insights and expands our understanding on the Hall effect of nonmagnetic semimetals.

Creating a heterostructure by combining two magnetically and structurally distinct ruthenium oxides is a crucial approach for investigating their emergent magnetic states and interactions. Previously, research has predominantly concentrated on the intrinsic properties of the ferromagnet SrRuO3 and recently discovered altermagnet RuO2 solely. Here, we engineered an ultrasharp sublattice-matched heterointerface using pseudo-cubic SrRuO3 and rutile RuO2, conducting an in-depth analysis of their spin interactions. Structurally, to accommodate the lattice symmetry mismatch, the inverted RuO2 layer undergoes an in-plane rotation of 18 degrees during epitaxial growth on SrRuO3 layer, resulting in an interesting and rotational interface with perfect crystallinity and negligible chemical intermixing. Performance-wise, the interfacial layer of 6 nm in RuO2 adjacent to SrRuO3 exhibits a nonzero magnetic moment, contributing to an enhanced anomalous Hall effect (AHE) at low temperatures. Furthermore, our observations indicate that, in contrast to SrRuO3 single layers, the AHE of [(RuO2)15/(SrRuO3)n] heterostructures shows nonlinear behavior and reaches its maximum when the SrRuO3 thickness reaches tens of nm. These results suggest that the interfacial magnetic interaction surpasses that of all-perovskite oxides ( 5-unit cells). This study underscores the significance and potential applications of magnetic interactions based on the crystallographic asymmetric interfaces in the design of spintronic devices.

In Na-ion batteries,O3-type layered oxide cathode materials encounter challenges such as particle cracking,oxy-gen loss,electrolyte side reactions,and multi-phase transitions during the charge/discharge process.This study focuses on surface coating with NiTiO3 achieved via secondary heat treatment using a coating precursor and the surface material.Through in-situ x-ray diffraction(XRD)and differential electrochemical mass spectrometry(DEMS),along with crystal structure characterizations of post-cycling materials,it was determined that the NiTiO3 coating layer facilitates the forma-tion of a stable lattice structure,effectively inhibiting lattice oxygen loss and reducing side reaction with the electrolyte.This enhancement in cycling stability was evidenced by a capacity retention of approximately 74％over 300 cycles at 1 C,marking a significant 30％improvement over the initial sample.Furthermore,notable advancements in rate performance were observed.Experimental results indicate that a stable and robust surface structure substantially enhances the overall stability of the bulk phase,presenting a novel approach for designing layered oxide cathodes with higher energy density.

Interfacial strain engineering can induce structural transformation and introduce new physical properties into materials, which is an effective method to prepare new multifunctional materials. However, interfacial strain has a limited spatial impact size. For example, in 2D thin films, the critical thickness of biaxial strain is typically less than 20 nm, which is not conducive to the maintenance of a strained structure and properties in thick film materials. The construction of a 3D interface can solve this problem. The large lattice mismatch between the BaZrO3 thin film and the substrate can induce the out-of-phase boundary (OPB) structure, which can extend along the thickness direction with the stacking of atoms. The lattice distortion at the OPB structure can provide a clamping effect for each layer of atoms, thus expanding the spatial influence range of biaxial strain. As a result, the uniform in-plane strain distribution and strain-induced ferroelectricity (Pr = 13 μC/cm2) are maintained along the thickness direction in BaZrO3 films.

Objective Vortex beams with orbital angular momentum (OAM) have many unique properties compared to other beams, and their spiral wavefront structure and phase changes open up new dimensions for applications such as lithography, optical communication, optical trapping, and quantum entanglement. In recent decades, researchers have been exploring the linear and nonlinear transmission of the Laguerre-Gaussian ( LG) vortex beam in media, and the coverage has been continuously expanded, which lays a solid foundation for developing the optical vortex. Most relevant research focuses on analyzing the properties of vortex beams and their linear transmission and evolution. However, the ultrashort pulse vortex laser has become a research hotspot with extensive studies. Since the inclusion of nonlinear processes will greatly increase the complexity of vortex beam analysis, the study on transmission and evolution of ultrashort pulse vortex lasers in nonlinear media is still rare. Thus, we experimentally investigate the propagation of mid-infrared LG beams in organic crystal DSTMS due to the cubic-quintic nonlinear effect and analyze the differences in the effect of polarization of the incident vortex beam on the transverse light field distribution. Methods High power mid-infrared optical parametric amplifier (OPA) pulses with 1450 nm center wavelength, 60 fs pulse duration, and 1 kHz repetition rate serve as the pump of the system. After passing through a customized spiral phase plate (SPP), the mid-infrared laser light is modulated into vortex beams and incident perpendicularly onto the surface of an organic crystal with a 640 mu m thickness. A 4f imaging system is constructed using two lenses to conduct imaging on the spot in either plane perpendicular to the light propagation direction within the crystal. The CCD camera moves back and forth in the horizontal direction to observe and record the spot evolution of the vortex beam during propagation, starting from the rear surface of the crystal. Results and Discussions In the experiment, the spot changes of mid-infrared vortex light before and after passing through the DSTMS crystal are found and compared with those of the BBO crystal to analyze the spot characteristics of the vortex beam after passing through different crystals. After passing through the BBO crystal, there is still only one bright ring in the spot, with the spot radius almost unchanged. However, after passing through the DSTMS crystal, the spot changes significantly from the original doughnut structure to three thin bright rings, and the number of rings increases. This is due to the nonlinear process of three-photon absorption of pump light by the DSTMS crystal. When the pump light polarization fulfills the optimal THz generation conditions, the nonlinear refractive index of DSTMS mainly originates from the quasi-chi((3)) effect due to a combination of the cascaded 2nd-order OR process and the linear EO effect. The contribution from the intrinsic chi((3)) nonlinearity of DSTMS should be negligible. Its additional nonlinear refractive index causes the refractive index of the pump light to vary with light intensity, which in turn leads to spectrum broadening. For each spectral component generated after the spectrum broadening of the incident LG beam in the Kerr medium, its respective corresponding LG mode has the same topological charge and radial index. As the frequency value of each spectral component is different, the respective corresponding Rayleigh length and beam waist position are different to bring various light field expressions for the LG vortex beam corresponding to each spectral component. Therefore, the corresponding brightest rings have different radii, and each bright ring generally does not coincide with each other in the observation plane, resulting in a weak spot intensity in most regions of the observation plane. To verify the above optical spot evolution process, we can simulate the light field distribution of the LG beam before and after passing through the DSTMS medium with a Kerr-like effect by MATLAB simulation analysis based on the generalized Gaussian beam decomposition method, with the simulation results shown in Fig. 3. Fig. 3(c) reveals that the effect of the Kerr medium on the incident LG beam is to produce LG beams with different radial modes. Meanwhile, the effect of the polarization of the incident vortex light on the spot of the outgoing light from the rear surface of the crystal is further investigated experimentally, and the experimental results illustrate that the incident light with different polarization produces vortex beams with different light intensity distributions. Conclusions We research the evolutionary mechanism of vortex beams in nonlinear organic crystal DSTMS initially, showing that the nonlinear transmission effect can change the light intensity distribution of vortex beams to a large extent. The generalized Gaussian beam decomposition method is utilized to simulate and analyze the light intensity distribution of the LG beam before and after passing through the medium with a Kerr- like effect, which indicates that the Kerr medium affects the incident LG beam by producing LG beams with different radial modes. Additionally, the effect of different polarization of the incident vortex light on vortex mid-infrared laser transmission in DSTMS is studied to demonstrate the effect of nonlinear transmission on the LG beam.

Electric field control of the magnetic state in ferrimagnets holds great promise for developing spintronic devices with lower power consumption due to their reduced net magnetization compared with that in ferromagnets and the lack of heating induced in the case of current-induced magnetization switching. Here, we study heterostructures made from piezoelectric and ferrimagnetic materials (Pb (Zr0.2Ti0.8) O3 (PZT)/CoGd) and demonstrate the non-volatile reversal of the perpendicular net magnetization in the CoGd ferrimagnet by manipulating the electric-field-driven polarization within the PZT layer. Electron energy loss spectra and the X-ray absorption spectrum directly verify that the oxygen ion migration at the PZT/CoGd interface associated with reversing the polarization causes enhanced or reduced oxidation in CoGd. Ab initio calculations further substantiate that the migrated oxygen ions can modulate the relative magnetization of Co/Gd sublattices, facilitating perpendicular net magnetization switching. Our findings offer an approach to effectively control ferrimagnetic net magnetization, holding significant implications for ferrimagnetic spintronic applications.

Field-free switching of a perpendicularly magnetized heavy metal/ferromagnetic metal bilayer or single alloy layer through spin-orbit torque (SOT) provides a potential way for next-generation spintronic devices with fast speed and high efficiency. Here, a sizable symmetry dependence of field-free magnetization switching via an out-of-plane torque in CoxPt100-x single layers is reported. It is found that the sign of in-plane SOT in CoxPt100-x when x <= 25 is positive. However, it changes to negative when x > 25, while the out-of-plane SOT changes its sign when x > 30. The polarized neutron reflectometry measurement further suggests an interface layer with rich Pt content near the substrate, which could have a strong interface effect on the out-of-plane SOT. The sign of the out-of-plane SOT, and then the polarity of the field-free magnetization switching, is determined by the competition between the out-of-plane torques arising from the bulk and interface parts in the CoxPt100-x single layers. It is expected that such interface effect of the out-of-plane torque is desirable to the applications in spin logic devices using symmetry dependence of field-free magnetization switching in the ferromagnetic CoPt single layers.

Electrochemical-mechanical coupling poses enormous challenges to the interfacial and structural stability but create new opportunities to design innovative all-solid-state batteries from scratch. Relying on the solid-solid constraint in the space-limited domain structure, we propose to exploit the lithiation-induced stress to drive the active materials creep, thereby improving the structural integrity. For demonstration, we fabricate the creep-type all-solid-state cathode using creepable Se material and an all-in-one rigid ionic/electronic conducting Mo6Se8 framework. As indicated by the in-situ experiment and numerical simulation, this cathode presents unique capabilities in improving interparticle contact and avoiding particle fracture, leading to its superior electrochemical performance, including a superior long-cycle life of more than 3000 cycles at 0.5 C and a high volumetric energy density of 2460 Wh/L at the cathode level. We believe this innovative strategy to utilize mechanics to boost the electrochemical performance could shed light on the future design of all-solid-state batteries for practical applications. Electrochemical-mechanical issues bring challenges but create new opportunities to design innovative all-solid-state batteries. Here, the authors propose to use the (de)lithiation-stress-creep synergistic time-dependent evolution to boost the electrochemical performance of all-solid-state batteries.

The layered Mn-rich oxide cathode materials with oxygen redox activity are highly appealing in sodium-ion (Na-ion) batteries because of their high energy density and low cost. However, the applications of such materials are hindered by issues such as low Mn redox potential and irreversible phase transformation. Rational modulation of the ordering of the transition metal (TM) layer can inhibit the constraints and stabilize the anionic redox reactions. Herein we introduce stable Li/Mn anti-siting in the TM layer of P2-type Na0.6Li0.2Mn0.8O2 as a strategy to create abundant Mn sites and O sites that are inequivalent to the counterpart of each in the lattice, and thus to prompt the diverse Mn and O redox. The self-locking of the anti-siting energetically inhibits the P2-O2 phase transformation and the resultant structural degradations. In addition, such modulation activates more Mn in charge compensation at high potentials. As a result, this regulation increases the reversible capacity from 104.2 mAh g−1 to 153.7 mAh g−1 and enhances the cycling stability of Na0.6Li0.2Mn0.8O2. This anti-siting strategy offers a new solution to designing cathode materials with high structural stability and high energy density.

The fluorite ferroelectrics is extremely promising for memory applications due to the silicon compatibility and the robust ferroelectricity with decreasing size. However, the direct observation of local electronic polarization remains elusive, thereby hindering the comprehension of the atomic-scale origin of ferroelectricity. Here, we directly map the real-space charge density of the ZrO2 nanocrystal in its polar, nonpolar, as well as interphase regions with sub-Ångström resolution by four-dimensional scanning transmission electron microscopy (4D-STEM). Based on the variation of the electric dipole moments, we analyze the electronic contribution to the total spontaneous polarization, which reaches a maximum of 17.8%. In comparison to the continuous polarization in conventional ferroelectric units, the local polarization profile looks like a maple leaf edge at the tetragonal-orthorhombic phase interface, which suggests a gradual increase in the electronic polarization and the covalent nature of the Zr-O bond. We validate these findings with 4D-STEM simulations and calculations based on density functional theory. These findings provide atomic insights into the bonding nature and phase transition feature in fluorite oxides, and unravel the likely origin of ferroelectricity in ferroelectrics.

High-voltage phase transition constitutes the major barrier to accessing high energy density in layered cathodes. However, questions remain regarding the origin of phase transition, because the interlayer weak bonding features cannot get an accurate description by experiments. Here, we determined van der Waals (vdW) interaction (vdWi) in Li x CoO 2 via visualizing its electron density, elucidating the origin of O3─O1 phase transition. The charge around oxygen is distorted by the increasing Co─O covalency. The charge distortion causes the difference of vdW gap between O3 and O1 phases, verified by a gap corrected vdW equation. In a high charging state, excessive covalency breaks the vdW gap balance, driving the O3 phase toward a stable O1 one. This interpretation of vdWi-dominated phase transition can be applied to other layered materials, as shown by a map regarding degree of covalence. Last, we introduce the cationic potential to provide a solution for designing high-voltage layered cathodes.