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Two-dimensional (2D) materials embedded in magnetic tunnel junctions (MTJs) provide a platform to increase the control over spin transport properties by the proximity spin-filtering effect. This could be harnessed to craft spintronic devices with low power consumption and high performance. We explore the spin transport in the 2D MTJs based on graphene, which is uniformly grown on Ni(111) substrates using the chemical vapor deposition technique. After the Ni thin film is deposited bottom–up on the well-grown Ni(111)/graphene surface in an e-beam evaporation system by the physical vapor deposition method, the Ni/graphene/Ni nanojunction array devices are successfully prepared by using nanography technology. Evidence of the emergence of tunneling magnetoresistance (TMR) effects with ultrasmall resistance × area products in graphene-based nanojunctions is observed by the exclusion of anisotropic magnetoresistance. The theoretical analysis shows that this TMR is mainly attributed to the strong spin-filtering effect at the perfect Ni(111)/graphene interface. Besides, earlier findings indicate that the TMR would be promoted more effectively if the short-circuit effect formed in the process of nanographic etching by an ion beam can be further eliminated. Overall, this study provides a path to harness the full potential of graphene-based MTJ array devices with a high efficiency and performance.

Underwater flexible sensors have a future for wide application, which is promising for attaching them to underwater creatures to monitor vital signals and biomechanical analysis of their motion and perceive tiny environmental disturbances. However, the pressure waves induced by biological swimming are extremely weak and susceptible to undercurrents, making them difficult to sense. Here, we report an ultrahighly sensitive biomimetic electronic fish skin designed by embedding an artificial pseudocapacitive-based hair cell into a simulated canal neuromast encapsulation structure, in which the artificial hair cell, as the key sensitive unit, is assembled from hybrid film electrodes and polyurethane–acidic electrolyte foam. Such a film is prepared by inter-cross-linking MXene and holey reduced graphene oxide with the assistance of l-cysteine, effectively increasing the interfacial capacitance and alleviating the oxidation issues of MXene. Meanwhile, the acidic foam with high porosity shows great compressibility to adapt to a high-pressure underwater environment. Consequently, the device exhibits ultrahighly sensitivity (maximum sensitivity ∼173688 kPa–1) over a wide range of depths (0–100 m) and remains stable after 10000 repeated tests. As an example case, the device is integrated as a motion monitoring system to identify the minor disturbances triggered by instantaneous postural changes of fish. The electronic fish skin is expected to demonstrate enormous potentials in flow field monitoring, ocean current detecting, and even seismic waves warning.

Size-resolved aerosols collected at Tianjin, North China in winter were studied for inorganic ions, carbonaceous components, dicarboxylic acids, benzoic acid, oxocarboxylic acids and α-dicarbonyls. Na+found to be the dominant ions, while sum of SO42−, NO3−and NH4+was almost more than half of the total ionic mass in all size fractions. Both inorganic anions and carbonaceous components showed a bimodal distribution. Water-soluble organic carbon (WSOC) accounted for 53.9% to total OC, with 36.0% in fine- and 17.9% in coarse-mode fractions (≤ 2.1 and ≥ 2.1 μm particles, respectively) of aerosols. Most of dicarboxylic acids and related compounds peaked at 0.43–0.65 μm size bin followed by a gradual decrease, except for few species. Average concentrations of total dicarboxylic acids were 1223 and 516 ng m−3in fine and coarse mode fractions, respectively. Oxalic acid found to be the most abundant species followed by phthalic and azelaic acids in fine- and coarse-mode fractions, except the third most abundance of glyoxylic acid in the coarse mode fraction. Based on size-resolved distributions, correlations and mass ratios of selected marker species, we found that inorganic aerosols were mainly derived from sea salt and vehicular exhaust and coal combustion emissions rather than biomass burning and soil dust in winter over the Tianjin region, North China. While dicarboxylic acids and related compounds were mainly originated from fossil fuel including coal combustion and their contributions from biomass burning and marine and terrestrial biogenic emissions were minor. Their in situ secondary formation and transformations were intensive at local and regional scales.

Superconductor/magnetoresistance (SC/MR) mixed sensor has the advantage of ultrahigh sensitivity and is thought to be a promising candidate for weak magnetic field detection. However, it has no effect on the magnetic field in the superconducting flux-to-field transformation amplifier (SFTA) plane, which limits its applications in 3-D magnetic field detection. Here, we present a new architecture of SC/MR mixed sensor with only one integrated magnetic concentrator (IMC) to realize the in-plane magnetic field measurement. Firstly, the conversion efficiency, defined as the in-plane magnetic changing to the out-plane magnetic field by the IMC and SFTA of mixed sensor, was systematically studied by the finite element analysis method, the results show that the high conversion efficiency is from the combined action of superconducting diamagnetism and magnetic concentrator of soft magnetic materials. Then, a serial prototype mixed sensors with different IMC relative configuration sizes were prepared and their experimental performances were obtained. Indeed, the mixed sensor with IMC can simultaneously measure the in-plane and out-of-plane magnetic fields, furthermore, the conversion efficiency changes as the function of the relative configuration size is consistent well with the simulation result. Finally, a three-axis SC/MR mixed sensor scheme and its corresponding three-axis magnetic field decoupling method based on this method were also proposed, showing the obvious capability of three-axis magnetic field measurement. Our work is meaningful to the development of a three-axis weak magnetic field detection.

MnBi2Te4(MBT) is the first intrinsic magnetic topological insulator with the interaction of spin-momentum locked surface electrons and intrinsic magnetism, and it exhibits novel magnetic and topological phenomena. Recent studies suggested that the interaction of electrons and magnetism can be affected by the Mn-doped Bi2Te3phase at the surface due to inevitable structural defects. Here, we report an observation of nonreciprocal transport, that is, current-direction-dependent resistance, in a bilayer composed of antiferromagnetic MBT and nonmagnetic Pt. The emergence of the nonreciprocal response below the Néel temperature confirms a correlation between nonreciprocity and intrinsic magnetism in the surface state of MBT. The angular dependence of the nonreciprocal transport indicates that nonreciprocal response originates from the asymmetry scattering of electrons at the surface of MBT mediated by magnon. Our work provides an insight into nonreciprocity arising from the correlation between magnetism and Dirac surface electrons in intrinsic magnetic topological insulators.

To understand the characteristics of chemical components and dicarboxylic acids, oxocarboxylic acids and α‐dicarbonyls in atmospheric aerosols at underground coal fire environment, we collected fine aerosols (PM2.5) from Wuhai, Inner Mongolia, North China, where the underground coal fire often occurs. PM2.5samples were analyzed for the measurements of carbonaceous components, stable carbon isotopic composition (δ13C) of total carbon, and molecular distribution and compound‐specific δ13C of diacids, oxoacids and α‐dicarbonyls. Oxalic acid (C2) was the most abundant species, accounting for 43.2%–63.1% (avg. 50.8%) of total diacids, followed by phthalic acid (Ph) (13.7%). Azelaic acid (C9) was the third most (7.4%) abundant, followed by succinic (C4) and malonic (C3) acids. Significant correlations of C2diacid with glyoxylic (ωC2) and 3‐oxopropanoic (ωC3) acids and C3diacid and their δ13C implied that diacids and related compounds were mainly derived from the underground coal fire emissions and subsequent in situ secondary formation. Based on molecular distribution, seasonal pattern and linear relations of C9diacid with C2, C3, ωC2and ωC3as well as with Ph acid and total diacids, together with the comparability and similarity of its δ13C (−27.0 ± 0.9‰) with that of Ph acid and organic matter in coals, respectively, we found that the C9diacid has been mainly derived from its precursors such as unsaturated fatty acids emitted from underground coal fires and their subsequent in situ photochemical oxidation. However, further research is needed to confirm such an importance of coal combustion for azelaic acid loading in atmospheric aerosols. Fine aerosols in the atmosphere cause high uncertainty in radiative forcing of the Earth's climate system and have become one of the serious environmental risk factors, causing more than 6 million premature deaths annually. The atmospheric environment over the underground coal fire field is different from that in urban area, because the emission of inorganic gaseous species, volatile organic compounds and particulates that consist oxygen‐containing organic species and polycyclic aromatic hydrocarbons and their subsequent photochemical oxidation processes are relatively larger at the coal fire field. Our study on fine aerosols from underground coal fire field at Wuhai, North China showed a rather large abundance of dicarboxylic acids associated with a specific partitioning from the coal fires compared to observations from other environments including an unusual abundance of azelaic acid. The characteristics of diacids in atmospheric aerosols at underground coal fire environment have been investigatedAzelaic acid could be applied in evaluating the coal combustion influence on secondary organic aerosols in the atmosphereC2was mainly derived from underground coal fire emissions and their subsequent in situ photochemical oxidation The characteristics of diacids in atmospheric aerosols at underground coal fire environment have been investigated Azelaic acid could be applied in evaluating the coal combustion influence on secondary organic aerosols in the atmosphere C2was mainly derived from underground coal fire emissions and their subsequent in situ photochemical oxidation

Shear stirrups in a prestressed ultra-high performance concrete (UHPC) beam might be eliminated due to the high tensile strength of UHPC. This research aims to investigate shear behavior of the externally prestressed UHPC beams without stirrups. Thirteen UHPC beams were tested with the experimental parameters of prestressing level, shear span-to-depth ratio, longitudinal reinforcement ratio, fiber content, and stirrup ratio. The results showed that the beam with the longitudinal reinforcement ratio of 2.0 % under a shear span-to-depth ratio of 2.0 failed in flexure, even though additionally applying a higher prestressing up to 40 % of tensile strength of prestressing tendon. However, the externally prestressed UHPC beams under a shear span-to-depth ratio lower than 2.0 failed in shear. The shear strength of UHPC beam increased with a higher prestressing, lower shear span-to-depth ratio, more longitudinal reinforcements and stirrups, and higher fiber content. French Standard formula and PCI formula for shear design were conservative, irrespective of the existence or absence of stirrups in the prestressed UHPC beam. The calculated results indicated that the externally prestressed UHPC beams met the requirement of shear design codes when no stirrup was employed.

Magnetically powered miniature robots have received increasing attention for decades owing to their convenient navigation ability, noninvasive remote actuation, and diverse potential applications. Although various individual motions of magnetic miniature robots have been explored, mimicking group cooperation and synchronized coordination of natural intelligence remain challenging. Here, we introduce diverse cooperative behaviors between two magnetic miniature swimmers in uniform magnetic fields by tuning and composing their magnetic moments. The ability of these magnetic miniature swimmers to form dynamic steady states offers considerable promise for creating groups of machines that can perform cooperative tasks.

Strain-mediated ferromagnetic/ferroelectric (FE) heterostructures have played an important role in multiferroic materials to investigate the electric-field control of magnetism in the past decade, due to their excellent performances, such as room-temperature operation and large magnetoelectric (ME) coupling effect. Because of the different FE-switching-originated strain behaviors and varied interfacial coupling effect, both loop-like (nonvolatile) and butterfly-like (volatile) converse ME effects have been reported. Here, we investigate the electric-field control of magnetism in a multiferroic heterostructure composed of a polycrystalline Fe thin film and a Pb(Mg1/3Nb2/3)0.7Ti0.3O3single crystal, and the experimental results exhibit complex behaviors, suggesting the coexistence of volatile and nonvolatile converse ME effects. By separating the symmetrical and antisymmetrical parts of the electrical modulation of magnetization, we distinguished the loop-like hysteresis and butterfly-like magnetization changes tuned by electric fields, corresponding to the strain effects related to the FE 109° switching and 71/180° switching, respectively. Further magnetic-field-dependent as well as angular-dependent investigation of the converse ME effect confirmed the strain-mediated magnetism involving competition among the Zeeman energy, magnetocrystalline anisotropy energy, and strain-generated magnetoelastic energy. This study is helpful for understanding the electric-field control of magnetism in multiferroic heterostructures as well as its relevant applications.

Intrinsic spatial inhomogeneity or phase separation in cuprates, manganites, etc., related to electronic and/or magnetic properties, has attracted much attention due to its significance in fundamental physics and applications. Here we use scanning Kerr microscopy and scanning electron microscopy with polarization analysis with in situ electric fields to reveal the existence of intrinsic spatial inhomogeneity of the magnetic response to an electric field on a mesoscale with the coexistence of looplike (nonvolatile) and butterfly-like (volatile) behaviors in Co40Fe40B20/Pb(Mg1/3Nb2/3)0.7Ti0.3O3ferromagnetic/ferroelectric (FM/FE) multiferroic heterostructures. Both the experimental results and micromagnetic simulations suggest that these two behaviors come from the 109° and the 71°/180° FE domain switching, respectively, which have a spatial distribution. This FE domain-switching-controlled magnetism is significant for understanding the nature of FM/FE coupling on the mesoscale and provides a path for designing magnetoelectric devices through domain engineering.

Flexible pressure sensors developed rapidly with increased sensitivity, a fast response time, high stability, and excellent deformability. These progresses have expanded the application of wearable electronics under high-pressure backgrounds while also bringing new challenges. In particular, the nonlinearity and narrow working range lead to a gradually insensitive response, principally because the microstructure deforms inconsistently on the device interfaces in the whole working range. Herein, we report an ionic flexible sensor with a record-high linearity (R2= 0.99994) in a wide working range (up to 600 kPa). The linearity response comes from the normal-direction graded hemisphere (GH) microstructure. It is prepared from poly(dimethylsiloxane) (PDMS)/carbon nanotubes (CNTs)/Au into flexible and deformable electrodes, and its geometry is precisely designed from the linear elastic theory and optimized through finite element simulation. The sensor can achieve a high sensitivity of S= 165.5 kPa–1, a response-relaxation time of <30 ms, and superb consistency, allowing the device to detect vibration signals. Our sensor has been assembled with circuits and capsulation in order to monitor the function state of players in underwater sports in the frequency domain. This work deepens the theory of linearized design of microstructures and provides a strategy to make flexible pressure sensors that have combined the performances of ultrahigh linearity, high sensitivity, and a wide working range.

Electric-field control of magnetism in multiferroic heterostructures composed of Co40Fe40B20(CoFeB) and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-xPT) with different ferroelectric phases via changing composition and temperature is explored. It is demonstrated that the nonvolatile looplikebipolar-electric-field-controlled magnetization, previously found in the CoFeB/PMN-xPT heterostructures with PMN-xPT in the rhombohedral (R) phase around the morphotropic phase boundary (MPB), also occurs for PMN-xPTs with both R phase (far away from MPB) and monoclinic (M) phase, suggesting that the phenomenon is the common feature of CoFeB/PMN-xPT multiferroic heterostructures for PMN-xPT with different phases. The magnitude of the effect changes with increasing temperature and volatile bipolar-electric-field-controlled magnetization with a butterflylikebehavior occurs when the ferroelectric phase changes to the tetragonal phase (T). Moreover, for the R-phase sample with x = 0.18, an abrupt and giant increase of magnetization is observed at a characteristic temperature in the temperature dependence of magnetization curve. These results are discussed in terms of coupling between magnetism and ferroelectric domains including macro- and microdomains for different ferroelectric phases. This work is helpful for understanding the phenomena of electric-field control of magnetism in FM/FE multiferroic heterostructures and is also important for applications.

To better understand the characteristics and sources of water‐soluble organic aerosols (OA) under different weather conditions, we collected fine aerosols (PM2.5) at an urban (ND) and a suburban (HEP) sites in Tianjin, North China over a 1‐year period and studied for diacids, oxoacids, and α‐dicarbonyls. Oxalic acid was found to be the most abundant (55.8 %± 10.7% at ND and 60.7% ± 13.0%) species during the campaign, followed by succinic and malonic acids, except for winter, in which phthalic acid was the third most abundant species at both the sites. Glyoxylic acid was found to be the most abundant (∼42%) oxoacids. Concentrations of diacids (range: 96.0–2137 ng m−3at ND and 185–1227 ng m−3at HEP) and related compounds were much higher in winter and lower in summer. Whereas the mass fractions of total diacids in PM2.5and their carbon contents in TC, OC, and WSOC were 2–3 times higher in summer than that in winter. Based on seasonal variations in mass ratios, relative abundances and linear relations of selected marker species including nss‐K+, we found that water‐soluble OA over the Tianjin region were mainly derived from fossil fuel including coal combustion and biomass burning emissions and subsequent intensive photochemical processing in the atmosphere. The linear relations of diacids with ambient temperature, RH, SO42−and oxidants (O3and NO2) and SO2inferred that secondary formation and transformations of water‐soluble OA, particularly diacids and related compounds, in aqueous phase were more effective in cold period (October‐February), whereas in gas phase in warm period (March–September). Diacids and related compounds were characterized in fine aerosols (PM2.5) from Tianjin, North China over a 1‐year periodFossil fuel combustion and biomass burning emissions and secondary processes are the major sources of organic aerosols (OA) in North ChinaGaseous and aqueous phase secondary processes are the major formation pathways of water‐soluble OA in warm and cold periods, respectively Diacids and related compounds were characterized in fine aerosols (PM2.5) from Tianjin, North China over a 1‐year period Fossil fuel combustion and biomass burning emissions and secondary processes are the major sources of organic aerosols (OA) in North China Gaseous and aqueous phase secondary processes are the major formation pathways of water‐soluble OA in warm and cold periods, respectively

In-sensor computing implemented by novel neuromorphic devices has been regarded as the potential technology to break the acquisition wall. Moreover, the nonlinear convolution inspired by the biological neural system outperforms the traditional linear convolution. Therefore, realizing the in-sensor nonlinear convolutional processing with the intrinsic nonlinearity of novel neuromorphic devices would be exciting and hardware friendly. Here, a new type of in-sensor nonlinear convolutional processing architecture is proposed based on STT-MTJ (spin transfer torque-magnetic tunnel junction) devices and simple peripheral circuits. The nonlinear dynamic characters of the STT-MTJ device are regulated by bias currents and magnetic fields. Meanwhile, the hybrid STT-MTJ/CMOS (complementary metal oxide semiconductor) circuit exhibits nonlinear dependence of the output voltage on bias currents and magnetic fields. In this way, a nonlinear convolutional unit is developed by the inherent property of hardware. Based on the in-sensor nonlinear convolutional unit, a convolutional network is simulated to perform the classification task, and a high accuracy is realized. This work indicates that the in-sensor nonlinear convolution offers a promising way to develop in-sensor computing at the edge intelligence devices. [ABSTRACT FROM AUTHOR]