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Consistent c-axis orientation characteristics toward the direction of applied pressure of Y-type BaSrCo2Fe11AlO22 (BSCFAO-θ) were successfully prepared by the strategy of hot pressing. The samples' magnetoelectric coupling performance was greatly enhanced by the strategy of hot pressing than that of the traditional solid reaction method. The magnetoelectric current of BSCFAO-θ (θ = 0°) (12.06 μA/m2) was nearly 5 times higher than BSCFAO-SS (2.24 μA/m2). The magnetoelectric polarization of BSCFAO-θ (θ = 0°) (32.82 μC/m2) was nearly 4 times higher than that of BSCFAO-SS (8.31 μC/m2). The magnetoelectric coupling coefficients of BSCFAO-θ (θ = 0°) (1880 ps/m) were nearly 4 times higher than those of BSCFAO-SS (404 ps/m). The enhancement of magnetoelectric polarization of BSCFAO-θ (θ = 0°) can be attributed to the uniform c-axis orientation, which reinforced magnetoelectric polarization compared with none orientation that eliminated the magnetoelectric polarization on grain boundaries. The magnetoelectric coupling performance of BSCFAO-θ presented a gradually decreasing trend with the angle changing from 0° to 90° for the changing of orientation. Compared with traditional solid reaction methods, the strategy of hot pressing inhibits grain growth and increases grain boundaries, thus facilitating the enhancement of grain boundaries' resistivity, and the electrical resistivity of BSCFAO-θ (3.08 × 1010 Ω cm) was nearly 10 000 times higher than that of BSCFAO-SS (2.5 × 106 Ω cm), which also benefits the magnetoelectric polarization performance of BSCFAO-θ. Therefore, the hot-pressing strategy can contribute to the forming of oriented ceramics and enhance the grain boundaries' resistivity to improve magnetoelectric coupling performance. [ABSTRACT FROM AUTHOR]

The plasma sheath causes the spacecraft’s communication signal to attenuate dramatically during the re-entry period, which seriously threatens the astronauts. However, valid experimental protocols have not been obtained hitherto. To realize the propagation of electromagnetic waves in negative permittivity background of the plasma sheath, alumina columns are embedded in the plasma background to form plasma photonic crystals, which can support the coupling of evanescent waves between the alumina columns. We experimentally demonstrate the realization of communication in blackout scenario by achieving a complete passing band in the plasma cutoff region. For high frequency communications in the plasma sheath, electromagnetic wave propagation based on topological edge states is also experimentally demonstrated. Furthermore, we realize a triply-degenerate Dirac cone formed dynamically at the center of the Brillouin zone by modulating the electron density, where electromagnetic wave exhibits high transmittance and does not experience phase accumulation at the Dirac point. Our work thus not only provides an effective approach to overcome the communication blackout problem, but the design can also be served as a promising experimental platform to explore topological electromagnetic phenomena.

This paper has established a relatively comprehensive model for ultra-low frequency (ULF) current induced by thermal pressure gradients and its propagation. In the ULF current excitation model, we decomposed the current into a constant term unaffected by altitude and a product with a function significantly influenced by altitude. Combining this with the EISCAT background, we determined that for modulation frequencies below 5 Hz, the optimal height for ULF current excitation corresponds to the critical frequency height. We calculated the ionospheric currents at heating altitudes of 332 km for modulation frequencies of 5 Hz; the corresponding maximum currents were 1.03 × 10−10 A·m−2. By incorporating the current into the ULF waves propagation model based on magnetoionic theory, we found that the electromagnetic field energy is mainly concentrated in the horizontal direction, indicating that the energy primarily propagates outward through magnetosonic waves. The dominant components are the electric field component Ey and the magnetic field component Bz, whose maximum values reached 1.1 μV·m−1 and 1.5 pT. Unfortunately, magnetosonic waves cannot propagate downward due to the sharp variation in the real part of the refractive index between 200 and 300 km. However, the shear Alfvén waves component By can propagate downward, and there is still an intensity of approximately 0.1 pT at the bottom of the ionosphere, which is because the refractive index of shear Alfvén waves is most uniform in the parallel magnetic field direction, allowing By to propagate parallel to the magnetic field effectively. [ABSTRACT FROM AUTHOR]

A sub-wavelength particle with a total scattering cross section that exceeds the single channel limit is referred to as a superscatterer, which can provide ability to control light in nanoscale. A variety of superscatter structures have been suggested, most of them are typically constructed with strong forward scattering but minor backscattering. This unusual behavior can be attributed to the superposition of resonant modes in adjacent angular momentum channels. We reveal the mechanism of super backscattering for subwavelength column, which can be formed by recombining non-adjacent resonant modes, as confirmed by our numerical analysis. [ABSTRACT FROM AUTHOR]

The twig edge states in graphene‐like structures are viewed as the fourth states complementary to their zigzag, bearded, and armchair counterparts. In this work, a rod‐in‐plasma system in a honeycomb lattice with twig edge truncation under external magnetic fields and lattice scaling is studied and it is shown that twig edge states can exist in different phases of the system, such as quantum Hall (QH) phase, quantum spin Hall (QSH) phase, and insulating phase. The twig edge states in the negative permittivity background exhibit robust one‐way transmission properties immune to backscattering and thus provide a novel avenue for solving the plasma communication blackout problem. Moreover, it is demonstrated that corner and edge states can exist within the shrunken structure by modulating the on‐site potential of the twig edges. Especially, helical edge states with the unique feature of pseudospin‐momentum locking that can be excited by chiral sources are demonstrated at the twig edges. These results show that the twig edges and interface engineering can bring new opportunities for more flexible manipulation of electromagnetic waves. [ABSTRACT FROM AUTHOR]

Doping is an effective strategy to modulate the dielectric behaviors of microwave absorption (MA) materials, for which the complex permittivity can be manipulated by encoding defect genes in the contracted crystal, while it is seldom illustrated in the magnetic ferrite crystal. Herein, the impact of defect genes on enhancing dielectric polarization in contracted Ba1–2xLaxSmxFe12O19 (LaSm-x) crystals has been investigated by lanthanum–samarium codoping BaFe12O19. It can be found that the MA character can be expressed via dielectric polarization instructed by defect genes, and their encoded amount can be guided through doping of various contents. Profiting from these enhanced point defects, enriched oxygen vacancies, and improved vacancies on the grain boundary, the intensified defect-induced polarization causes the highest dielectric loss angular tangent above 0.5 at most testing bands in LaSm-4 (the largest shrinkage factor of 4.57%). Accordingly, LaSm-4 is awarded for its optimized MA performance, embracing a minimum reflection loss of −62.8 dB and an effective absorption bandwidth of 5.64 GHz at 2.1 mm (12.05–17.69 GHz). This work clarifies the instructive impact of defect genes encoded in ferrites on enhancing polarization loss, providing a promising strategy to strengthen dielectric loss ability in other magnetic materials. [ABSTRACT FROM AUTHOR]

The discharge properties of post‐cathode plasma generated by grid electrode discharge were investigated. Post‐cathode plasma is the plasma, generated in an open discharge, at the other side of the cathode that is different from the electrode gap. Based on the unique electron transport, discharge chamber parameters were adjusted to compare their impact on the electron density of the post‐cathode plasma. The peak of the electron flow in the grid cathode hole and the peak of the post‐cathode plasma thickness appear in the same diameter of the grid electrode holes, which shows the crucial influence of the electron transport within the grid cathode on the post‐cathode plasma. The study also investigated the combined effects of cathode thickness and gas pressure on post‐cathode plasma thickness. The findings suggest that the primary factor influencing post‐cathode plasma thickness is the electron transport within the grid cathode. [ABSTRACT FROM AUTHOR]

The possibility of using plasma electron spectroscopy (PLES) as a practical method for the detection and identification of crystalline impurities of salts: silver salts, as well as ammonium salts, used in explosives and dangerous substances is shown. To create a prototype of the PLES detector, relatively simple technical solutions are adopted. The source of excitation of metastable atoms is a short DC glow discharge. For analysis, probe scheme for registering electric current from an auxiliary additional electrode probe is used when scanning the retarding electric potential. As a result of a series of experiments, the possibility of detecting products, cathode sputtering, and decomposition of ammonium and silver salts was shown. In particular, peaks from ammonia, nitrogen oxide, silver, and chlorine were recorded. [ABSTRACT FROM AUTHOR]

As a technology that can not only address water pollution but also generate ammonia, electrocatalytic reduction of nitrate (NO3RR) to ammonia has seen a new upsurge in recent years. Herein, through first-principles high-throughput screening, we discovered that g-C3N4-based dual-atom catalysts (M1M2/g-C3N4, M1 = M2 = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) exhibit extraordinary NO3RR catalytic performance. The multilevel descriptor elucidates the origin of the NO3RR reaction and facilitates rapid screening of candidate materials. The results indicate that TiFe/g-C3N4 possesses the best performance (UL = − 0.21 eV) among the 36 M1M2/g-C3N4 catalysts evaluated. Impressively, TiFe/g-C3N4 dual-atom catalysts differ from single-atom catalysts in that they follow a distinct dissociation–association reaction mechanism. Further orbital analysis signifies that this behavior arises from the synergistic effect of dual-atom metals. By establishing the correlation between structure and performance, our predictions contribute to the advancement of NO3RR as a method of ammonia production. This study holds promise for addressing water pollution while simultaneously harnessing renewable resources. [ABSTRACT FROM AUTHOR]

Suffering from the formation of metal-ion dendrites and low storage capacity, MXene materials exhibit unsatisfactory performance in Li and Na storage. In this study, we demonstrate that the MXene V3C2Cl2 structure can induce uniform Li and Na deposition. This is achieved through coherent heterogeneous interface reconstruction and regulated ion tiling by halogen surface termination. The high lattice matching (91% and 99%) between MXenes and Li/Na, along with positive Cl terminal regulation, guides Li/Na ions to nucleate uniformly on the V3C2Cl2 MXene matrix and grow in a planar manner. Cl termination proves effective in regulating Li/Na ions due to its moderate adsorption and diffusion coefficients. Furthermore, upon adsorption onto the Cl-terminated V3C2Cl2 monolayer, Li4 and Na4 clusters undergo dissociation, favoring uniform adsorption over cluster adsorption. V3C2Cl2 MXenes exhibit impressive Li/Na storage capacities of 434.07 mA h g−1 for Li and 217.03 mA h g−1 for Na, surpassing the Li storage capacity of Ti3C2Cl2 by three-fold and the Na storage capacity of V2C by 1.4 times. This study highlights the regulatory role of Cl surface terminals in dendrite formation and Li/Na ion deposition, with potential applications to other metal-ion storage electrodes. [ABSTRACT FROM AUTHOR]

Topological insulators exhibit great attraction in the fields of spintronics and quantum anomalous Hall effect, but their interaction with electromagnetic waves is rarely explored. Herein, topological insulator MnBi2Te4, synthesized via a solid-phase melting approach, was employed to compound with conductive materials. Benefiting from the unique topological untrivial property embodied in conductive topological surface state and ingenious composite microstructure, MnBi2Te4/carbon fibers displayed an efficient conductive network and high permittivity, obtaining an ultrathin electromagnetic wave absorption capacity with a maximum effective absorbing bandwidth of 2.6 GHz at 0.9 mm and a minimum reflection loss of −38.4 dB at 1.2 mm. More importantly, its effective absorbing peaks can cover 2–18 GHz through regulating its thickness, ranging from 0.8 to 6 mm. It is deciphered that topological insulators can retain the conductivity from conductive materials to a great extent and achieve distinct performances by compositing with materials of various microstructures. This work provides valuable insights into utilizing the unique advantages of topological insulators through compositing strategy and presents a precious approach for electromagnetic wave–absorbing composite materials. [ABSTRACT FROM AUTHOR]