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Abstract Exotic quantum states arise from the interplay of various degrees of freedom such as charge, spin, orbital, and lattice. Recently, a short-ranged charge order (CO) was discovered deep inside the antiferromagnetic phase of Kagome magnet FeGe, exhibiting close relationships with magnetism. Despite extensive investigations, the CO mechanism remains controversial, mainly because the short-ranged behavior hinders precise identification of CO superstructure. Here, combining multiple experimental techniques, we report the observation of a long-ranged CO in high-quality FeGe samples, which is accompanied with a first-order structural transition. With these high-quality samples, the distorted 2 × 2 × 2 CO superstructure is characterized by a strong dimerization along the c-axis of 1/4 of Ge1-sites in Fe3Ge layers, and in response to that, the 2 × 2 in-plane charge modulations are induced. Moreover, we show that the previously reported short-ranged CO might be related to large occupational disorders at Ge1-site, which upsets the equilibrium of the CO state and the ideal 1 × 1 × 1 structure with very close energies, inducing nanoscale coexistence of these two phases. Our study provides important clues for further understanding the CO properties in FeGe and helps to identify the CO mechanism.

Abstract Achieving effective manipulation of perpendicular exchange bias effect remains an intricate endeavor, yet it stands a significance for the evolution of ultra-high capacity and energy-efficient magnetic memory and logic devices. A persistent impediment to its practical applications is the reliance on external magnetic fields during the current-induced switching of exchange bias in perpendicularly magnetized structures. This study elucidates the achievement of a full electrical manipulation of the perpendicular exchange bias in the multilayers with an ultrathin antiferromagnetic layer. Owing to the anisotropic epitaxial strain in the 2-nm-thick IrMn3 layer, the considerable exchange bias effect is clearly achieved at room temperature. Concomitantly, a specific global uncompensated magnetization manifests in the IrMn3 layer, facilitating the switching of the irreversible portion of the uncompensated magnetization. Consequently, the perpendicular exchange bias can be manipulated by only applying pulsed current, notably independent of the presence of any external magnetic fields.

Abstract The manipulation of spin textures by spin currents is of fundamental and technological interest. A particularly interesting system is the 2D van der Waals ferromagnet Fe3GeTe2, in which Néel-type skyrmions have recently been observed. The origin of these chiral spin textures is of considerable interest. Recently, it was proposed that these derive from defects in the structure that lower the symmetry and allow for a bulk vector Dzyaloshinsky-Moriya interaction. Here, we demonstrate current-induced domain wall motion in Fe3GeTe2 flakes, in which the maximum domain wall velocity is an order of magnitude higher than those reported in previous studies. In heterostructures with Pt or W layers on top of the Fe3GeTe2 flakes, domain walls can be moved via a combination of spin transfer and spin-orbit torques. The competition between these torques leads to a change in the direction of domain wall motion with increasing magnitude of the injected current.

Abstract Developing efficient and economical electrocatalysts for acidic oxygen evolution reaction (OER) is essential for proton exchange membrane water electrolyzers (PEMWE). Cobalt oxides are considered promising non-precious OER catalysts due to their high activities. However, the severe dissolution of Co atoms in acid media leads to the collapse of crystal structure, which impedes their application in PEMWE. Here, we report that introducing acid-resistant Ir single atoms into the lattice of spinel cobalt oxides can significantly suppress the Co dissolution and keep them highly stable during the acidic OER process. Combining theoretical and experimental studies, we reveal that the stabilizing effect induced by Ir heteroatoms exhibits a strong dependence on the distance of adjacent Ir single atoms, where the OER stability of cobalt oxides continuously improves with decreasing the distance. When the distance reduces to about 0.6 nm, the spinel cobalt oxides present no obvious degradation over a 60-h stability test for acidic OER, suggesting potential for practical applications.

Abstract The metal-support interactions (MSI) could greatly determine the electronic properties of single-atom catalysts, thus affecting the catalytic performance. However, the typical approach to regulating MSI usually suffers from interference of the variation of supports or sacrificing the stability of catalysts. Here, we effectively regulate the site-specific MSI of Ir single atoms anchored on Ni layered double hydroxide through an electrochemical deposition strategy. Cathodic deposition drives Ir atoms to locate at three-fold facial center cubic hollow sites with strong MSI, while anodic deposition drives Ir atoms to deposit onto oxygen vacancy sites with weak MSI. The mass activity and intrinsic activity of Ir single-atom catalysts with strong MSI towards oxygen evolution reaction are 19.5 and 5.2 times that with weak MSI, respectively. Mechanism study reveals that the strong MSI between Ir atoms and the support stimulates the activity of Ir sites by inducing the switch of active sites from Ni sites to Ir sites and optimizes the adsorption strength of intermediates, thereby enhancing the activity.

A tremendous amount of research has witnessed the exploration of two-dimensional (2D) materials with intrinsic ferromagnetism and diverse physical properties. However, the low Curie temperature and deficient magnetic anisotropy hinder their practical applications in nanoscale spintronics. Based on first-principles calculations, we propose a new family of 2D ternary transition metal tellurides, CrX2Te4 (X = Al, Ga, and In), with both structural and magnetic stabilities at room temperature. Our calculations demonstrate that the 2D CrX2Te4 crystal exhibits the intrinsic 100% spin-polarized half-metallic feature with spin-up metallic and spin-down semi-conducting properties. With the remarkable magnetic moment of 4 μB per Cr atom, both 2D CrAl2Te4 and CrGa2Te4 crystals perform robust ferromagnetism with the out-of-plane magnetic anisotropy, while the 2D CrIn2Te4 crystal prefers the in-plane easy magnetization axis. The Monte Carlo simulation based on the 2D Heisenberg model shows that the critical Curie temperatures of the 2D CrAl2Te4, CrGa2Te4, and CrIn2Te4 crystals could reach 466, 431, and 536 K, respectively. Moreover, the magnetic exchange strength and magnetic anisotropy could be further enhanced by the in-plane biaxial strain. The novel electronic and magnetic features promote 2D CrX2Te4 (X = Al, Ga, and In) crystals as a new family of two-dimensional intrinsic ferromagnetic materials for next-generation advanced spintronics.

The influence of spin–orbit coupling (SOC) on ultrafast demagnetization dynamics is still an obscure issue. Ferromagnetic ternary alloy film containing Platinum element has the advantage that SOC strength can be regulated flexibly by varying the component ratio, thus is an excellent platform for investigating the dynamical effect of SOC. Here the fluence and component dependences of ultrafast demagnetization dynamics in ternary alloy L10-Fe0.5(Pd1-xPtx)0.5 films are studied by using time-resolved magneto-optical Kerr spectroscopy. An excitation-fluence dependent transition of demagnetization dynamics shows the Elliott-Yafet (EY) spin-flip scattering as the dominant mechanism of ultrafast demagnetization. We analyze the dynamics by a compatible fitting model and extract multiple characteristic time constants. It is clearly demonstrated that the gradual enhancement of SOC in fact decreases the spin-flip scattering and slow down the demagnetization process. We further show that the demagnetization time τm scales with the SOC strength ξ approximately under a dependence of τm∝ξ1/3, while a linear dependence exists between the spin–lattice relaxation time τs-l and ξ-6. These findings clarify the role of SOC in EY-dominated demagnetization dynamics and demonstrate an approach for tuning the speeds and duration of ultrafast demagnetization by regulating SOC strength.

Spin-orbit torques driven by the conventional spin Hall effect are widely used to switch magnetization, but this approach is nondeterministic and inefficient for magnets with perpendicular magnetic anisotropy. Here, the authors demonstrate deterministic, field-free switching in a Ni/Co multilayer by exploiting the magnetic spin Hall effect in adjacent Mn3Sn.

While single-atom catalysts offer well-defined structures, the homogeneity of the active sites is determined by localized coordination environments. Here, authors anchor Ir single atoms onto different sites on CoOOH and show how their distinct coordinations activate oxygen-evolving electrocatalysis

Abstract Coherent optical control of the magnetization in ferromagnetic (FM) mediums using ultrafast nonthermal effect paves a promising avenue to improve the speed and repetition rate of the magnetization manipulation. Whereas previously, only heat‐induced or helicity‐dependent magnetization dynamics are demonstrated in metallic ferromagnets. Here, the linearly‐polarized light control of magnetization is demonstrated in FM Co coupled with ferroelectric (FE) BiFeO3 by tuning the light polarization direction. It is revealed that in the Co/BiFeO3 heterostructure excited by femtosecond laser pulses, the magnetization precession amplitude follows a sinusoidal dependence on the laser polarization direction. This nonthermal control of coherent magnetization rotation is attributed to the optical rectification effect in the BiFeO3 layer, which yields a FE polarization depending on the light polarization, and the subsequent modulation of magnetic energy in Co by the electrostriction‐induced strain. This work demonstrates an effective route to nonthermally manipulate the ultrafast magnetization dynamics in metallic ferromagnets.

While single-atom catalysts exhibit intriguing catalytic performances and electronic structures, syntheses are often tailored to a particular system. Here, authors report electrochemical deposition as a universal approach for the fabrication of single-atom catalysts over range of metals and supports.

Electrocatalytic water splitting provides a renewable path to store energy in chemical bonds, but highly efficient oxygen-evolving catalysts in acid media remain limited. Here the authors report a quadruple perovskite ruthenate oxide as an effective and stable oxygen evolution electrocatalyst.

Neat well cement experience significant strength retrogression at high temperatures above 110 °C, especially at approximately 150 °C. To reveal the mechanism of performance degradation and guide the preparation of high-performance cement, we investigate the hydration process, mechanical behavior, and fracture process for well cement at the temperature of 150 °C based on molecular dynamics simulations and experiments. From triaxial pressure tests and Brazilian splitting tests, the strength, elastic modulus, and Poisson’s ratio of well cement decrease drastically with temperature increases from 80 °C to 150 °C. According to XRD, TG/DTG/DSC, and SEM, the hydration degree is insufficient, and larger pores exist in the microstructures. As the main binding phase of well cement, the mechanism of calcium silicate hydrates (C-S-H) influenced by curing temperatures is investigated through molecular dynamics simulations. C-S-H with calcium/silicon ratios (C/S) of 1.1 and 1.8 are simulated in the aqueous and solid states to investigate precipitation and mechanical behaviors. By reducing the C/S ratio to 1.1, the strength rebounds to a certain extent, and the adequacy of the hydration degree improved. It is found from the polymerization process that the increasing temperature promotes the polymerization rate, which is higher with C/S = 1.8 than that of 1.1. However, an increase in the C/S ratio will lead to a decrease in bridging oxygen content, thus a lower polymerization degree. The fracture simulations of C-S-H gels at different temperatures indicate that the failure of the C-S-H structure is mainly attributed to the disassembling of the calcium oxygen layers. With a higher temperature, there are fewer Ca-O bonds breaking, thus less strain energy consumed, resulting in worse performance. The elasticity of C-S-H, including Young’s and shear moduli, also exhibits certain degradations at a higher temperature. The elastic behavior of C-S-H with a low C/S ratio is generally higher than the high C/S.

Abstract Fe3GeTe2 is a promising candidate for van der Waals bonded ferromagnet because of its high Curie temperature and the prediction that its ferromagnetism can maintain upon exfoliating down to single layer. Here, we have reported the critical behavior to understand its ferromagnetic exchange. Based on various techniques including modified Arrott plot, Kouvel-Fisher plot, and critical isotherm analysis, a set of reliable critical exponents (β = 0.327 ± 0.003, γ = 1.079 ± 0.005, and δ = 4.261 ± 0.009) has been obtained. The critical behavior suggests a three-dimensional long-range magnetic coupling with the exchange distance decaying as J(r) ≈ r −4.6 in Fe3GeTe2. The possible origin of three-dimensional magnetic characteristics in van der Waals bonded magnets is discussed.

In this paper, sodium carbonate and calcium hydroxide instead of sodium hydroxide used as composite activators, and slag are applied to prepare one-part alkali-activated slag. Furthermore, the properties of the slag activated by sodium hydroxide are compared. The compressive strength, XRD, TGA, MIP, and SEM analysis of the two systems are performed. The results show that the one-part alkali-activated slag prepared from sodium carbonate and calcium hydroxide has a superior compressive strength against the slag activated by sodium hydroxide. It is also found that the hydration speed of the sodium hydroxide activated slag is faster, and thus the higher compressive strength of the one-part alkali-activated slag is not caused by the hydration speed. The hydration of one-part alkali-activated slag produces a certain amount of calcium carbonate, resulting in a lower porosity in comparison with the slag activated by sodium hydroxide, which may be the reason for the better compressive strength of one-part alkali-activated slag.

The activity of electrocatalysts exhibits a strong dependence on their electronic structures. Here, the authors manipulate the eg filling of perovskite cobaltite LaCoO3nanoparticles by changing particle size and show improved oxygen evolution activity with increased numbers of surface high-spin cobalt ions.

To overcome the fatigue safety problem of transmission tower cross arms caused by the wind-induced vibrations, an experimental study on the high-cycle fatigue performance of a new type of GFRP-steel sleeve composite cross arms was carried out. A total of six specimens were subjected to 500 thousand cyclic loadings based on the practical engineering background. The stress state was monitored, and a variety of load-displacement-time curves, the energy dissipation capacity, and the dynamic strain were analyzed to examine the effects of fatigue loading. After the fatigue test, the specimens without significant fatigue failure were evaluated to derive the residual bearing capacity. Based on the residual strength theory, the cumulative damage was examined, and the fatigue life was predicted under various loading conditions to ensure the reliability of composite cross arms. It is shown that the new type full-scale GFRP-steel sleeve composite cross arms can demonstrate a high level of safety redundancy on antifatigue performance and can be expected for wide application in power transmission towers.

In order to conduct high-precision measurement of the LIPS-300 ion thruster grid deformation in a vacuum, high-temperature, and plasma environment, a noncontact videometrics system using a telemicroscope was designed. Based on the captured image, the interactive partitioning edge detection method (IPEDM) was used to obtain stable and clear edges of multiple circular cooperative targets. Meanwhile, magnification factor calibration, rotation angle correction, and subpixel-level grid deformation measurement were performed with cooperative targets. The measurement results show that under the power of 750 W in the discharge chamber, the maximum thermal deformation of the screen grid is 1120 μm, and the gap between the screen grid and the accelerator grid is reduced by 420 μm. An accuracy assessment of the system shows that the grid deformation measurement accuracy is better than 12 μm, and the system satisfies the requirement of high-precision real-time measurements of the grid thermal deformation of the ion thruster under the discharge-chamber-running condition and the plasma-beam-extraction condition.

The ultrafast demagnetization dynamics of 3d and 4f spins, respectively, in FeCo and Tb of TbFeCo alloy film are studied independently by employing a dual-color time-resolved magneto-optical Kerr spectroscopy. The demagnetization dynamics of 3d and 4f spins are independently probed, respectively, by 800 and 400 nm light. Two-step demagnetization dynamics are observed for both the 3d and 4f spins under the excitation of 800 nm laser. In particular, the onset of 4f spin dynamics presents a delayed time with respect to the one of 3d spin dynamics. Those results clearly reveal a strong inter-atomic 3d–5d–4f exchange coupling which drives the first-step subpicosecond ultrafast demagnetization process of 4f spins, and a spin(4f)-lattice coupling which drives the second-step slower demagnetization process of 4f spins. A numerical calculation based on four temperature model reproduces the coupling characteristics in the demagnetization dynamics, and reveals the energy evolution dynamics among the different subsystems. These results provide a direct demonstration of strong coupling dynamics between the two spin subsystems in rare earth-transition metal alloy occurring within subpicosecond timescale, and show a new approach for ultrafast control of 4f spins via an indirect excitation.

In order to resolve the technical problem of cementing when drilling super high-pressure gas layers or saltwater layers of Guandu structure in Chishui region, Guizhou province, an ultra-heavy slurry was developed by optimizing weighting materials and designing particles, and applied to well Guanshen1 for liner cementing. According to the needs of preparing ultra-heavy slurry, the weighting additive MicroMAX in spherical particles was selected and combination of weight additives—reduced iron powder, iron powder, MicroMAX—was chosen for optimization. The particle size-distribution of the slurry was designed on the basis of the theory of tight packing, and the actual particle size-distribution is close to the ideal condition of tight packing. The ultra-heavy slurry with a density of 2.70-3.00 g/cm3 was designed, which is good in basic performance, flow ability and stability. In the simulated mixing test on the ground, a slurry with an average density of 2.71 g/cm3 was prepared by using conventional one-time cementing process. In the liner cementing of well Guanshen 1, the slurry with a density of 2.80 g/cm3 was used to successfully seal the super high-pressure saltwater layer: the average density of the slurry pumped into well was 2.78 g/cm3 and the maximum density was 2.82 g/cm3; amplitude log showed that the cementing quality was good; the well bore kept stable in follow-up drilling when the density of drilling fluid was reduced from 2.77 g/cm3 to 2.00 g/cm3. Key words: titania, photocatalysis, ceramic membrane, coupling reactor, methyl orange, degradation

Owing to their highly tailorable electrochemical characteristics and exceptional reactivity, high-entropy materials represent the next generation of water splitting catalysts. In this work, rare earth elements (Ho, Dy, Pr and Gd) were equivalently co-doped into the A-site of Y2Ru2O7, successfully resulting in a newtype high-entropy pyrochlore (Y0.2Ho0.2Dy0.2Gd0.2Pr0.2)2Ru2O7 (HE-YRO). The electrocatalyst presents an extremely low overpotential (η = 200 mV) and unobvious inactivation during stability testing at 10 mA cm−2 . More remarkably, at η = 270 mV, it shows an excellent inherent mass activity of 797.1 A gRu−1. By analyses of related pyrochlore oxides, several characteristics are confirmed for the HE-YRO electrocatalyst, which endow it with the high oxygen-evolution reaction (OER) performance. First of all, compared to those in YRO, more low-valent Ru3+ species and oxygen vacancies are induced in the HEYRO structure, which improves the performance. Secondly, inhibition of the grain coarsening is caused by the lattice distortion, which would lead to large surface areas for HE-YRO and then increase the OER active sites. Thirdly, the Ru 4d band is extended, which results in an enhancement of conductivity and a strengthened hybridization between O 2p and Ru 4d orbitals, and then improves the reaction kinetics of the OER. Therefore, the synergistic effect of the above factors that are induced by the equivalent multielement doping at the A-site results in the superior OER performance and chemical durability of the HE-YRO electrocatalyst for acid-water oxidation. This work not only presents a novel method for creating advanced materials for obtaining renewable and clean energy but also validates the efficacy of high-entropy design. [ABSTRACT FROM AUTHOR]