First Principle Study on Structural, Electronic, Magnetic, and Optical Properties of Co-Doped Middle Size Silver Clusters.

The structural, electronic, magnetic, and optical properties of Co-doped 10-20-atom silver clusters are investigated by GGA/PBE via the density functional theory. The Ag-Co clusters form core-shell structures with a Co atom in the center. Co atom doping modulates electronic properties like energy gap, molecular softness, global hardness, electronegativity, and electrophilicity index. For the optical spectra of the Ag-Co clusters, the energy of their spectra overall exhibits little change with increasing numbers of atoms; the strongest peaks are roughly distributed at 3.5 eV, and the intensity of their spectra overall is strengthened. Raman and vibrational spectra reflect structural changes with Co atom addition. The addition of the Co atom alters magnetic moments of specific Ag-Co clusters, while others remain unchanged.

Preparation of a novel foamed concrete modified with carbon fiber and graphite: Mechanical, electro-magnetic and microstructural characteristics based on X-CT.

In this paper, foam concrete is modified using graphite and carbon fiber as absorbents. The mechanical properties are analyzed in conjunction with hydration products, pore size distribution based on XCT test. Additionally, the resistivity, complex permittivity and complex permeability are tested. The results demonstrate that carbon fiber enhances the proportion of pores with diameters less than 200 µm in foam concrete, thereby significantly enhancing its flexural strength. Furthermore, incorporating graphite helps offset the initial retardation of sulfoaluminate cement hydration induced by carbon fibers, leading to an increase in the average pore size and a reduction in compressive strength. The incorporation of carbon fibers at a concentration of 0.6 wt% achieves the percolation threshold, akin to scenarios with singular fiber incorporation. Exceeding 2 wt% graphite content results in negligible influence on the conductivity. The synergistic integration of graphite and carbon fibers significantly improves the electromagnetic wave absorption performance of the composite. At a thickness of 6 mm, the material exhibits an effective bandwidth where the reflection loss is less than -10 dB, extending up to 2.5 GHz, which constitutes 52.08 % of the tested frequency spectrum.

Study on the Performance of a High-Speed Motor, Considering the Effect of Temperature on the Properties of High-Strength Non-Oriented Silicon Steel.

Considering the high-speed and high power density technical specifications of new energy vehicle motors, there is a growing demand for rotor strength as motor peak speeds reach 20,000 r/min and beyond. The utilization of non-oriented silicon steel with a high yield strength in rotors has emerged as a promising approach to increase motor speed. However, the magnetic and mechanical properties of high-strength silicon steel under variable temperature conditions have not been fully explored, particularly in regards to their impact on motor torque, efficiency, and speed. This manuscript investigates the behavior of high-strength silicon steel before and after annealing and at different temperatures, analyzing its influence on high-speed motor performance. The validity and feasibility of this study are confirmed through prototype testing, providing a comprehensive reference for engineering design.

Magnetic porous microspheres enhancing the anaerobic digestion of sewage sludge: Synergistic free and attached methanogenic consortia.

The addition of exogenous materials is a commonly reported method for promoting the anaerobic digestion (AD) of sludge. However, most exogenous materials are nano-sized and their use encounters problems relating to a need for continuous replenishment, uncontrollability and non-recyclability. Here, magnetic porous microspheres (MPMs), which can be controlled by magnetic forces, were prepared and used to enhance the methanogenesis of sludge. It was observed that the MPMs were spherical particles with diameters of approximately 100 µm and had a stable macroporous hybrid structure of magnetic cores and polymeric shells. Furthermore, the MPMs had good magnetic properties and a strong solid-liquid interfacial electron transfer ability, suggesting that MPMs are excellent carriers for methanogenic consortia. Experimental results showed that the addition of MPMs increased methane production and the proportion of methane in biogas from AD by 100.0 % and 21.2 %, respectively, indicating the MPMs notably enhanced the methanogenesis of sludge. Analyses of variations in key enzyme activities and electron transfer in sludge samples with and without MPMs in AD revealed that the MPMs significantly enhanced the activities of key enzymes involved in hydrolysis, acidification and methanation. This was achieved mainly by enhancing the extracellular electron transfer to strengthen the proton motive force on the cell membrane, which provides more energy generation for methanogenic metabolism. A careful examination of the variations in the morphology, pore structure and magnetism of the MPMs before and after AD revealed that the MPMs increased the prevalence of many highly active anaerobes, and that this did not weaken the magnetic performance. The microbial community structure and metatranscriptomic analysis further indicated that the acetotrophic methanogens (i.e., Methanosaeta) were mainly in a free state and that CO2-reducing methanogens (i.e., Methanolinea and Methanobacterium) mainly adhered to the MPMs. The above synergistic metabolism led to efficient methanogenesis, which indicates that the MPMs optimised the spatial ecological niche of methanogenic consortia. These findings provide an important reference for the development of magnetic porous materials promoting AD.

Magnetization Vector Rotation Reservoir Computing Operated by Redox Mechanism.

Physical reservoir computing is a promising way to develop efficient artificial intelligence using physical devices exhibiting nonlinear dynamics. Although magnetic materials have advantages in miniaturization, the need for a magnetic field and large electric current results in high electric power consumption and a complex device structure. To resolve these issues, we propose a redox-based physical reservoir utilizing the planar Hall effect and anisotropic magnetoresistance, which are phenomena described by different nonlinear functions of the magnetization vector that do not need a magnetic field to be applied. The expressive power of this reservoir based on a compact all-solid-state redox transistor is higher than the previous physical reservoir. The normalized mean square error of the reservoir on a second-order nonlinear equation task was 1.69 × 10-3, which is lower than that of a memristor array (3.13 × 10-3) even though the number of reservoir nodes was fewer than half that of the memristor array.

Stimuli-Induced Controls of Magnetic and Photophysical Properties Using Liquescent Open-Shell Ionic Molecular Systems.

This study explores the remarkable properties of liquescent open-shell ionic molecular systems, emphasizing the magnetic and photophysical characteristics arising from their associated structures in the condensed state under various conditions. Well-investigated open-shell molecules, namely, phenothiazine, dihydrophenazine, and tetrathiafulvalene radical cations, and bis(malononitriledithiolato)nickel(III) anionic complexes were examined, and the concept of liquescent open-shell ionic molecular systems was devised. Transformations in their associated structures are induced by external stimuli, resulting in significant variations in their physical properties. These experimental findings open new avenues for exploring and applying stimuli-responsive molecule-based materials.

Stoichiometry-Tunable Synthesis and Magnetic Property Exploration of Two-Dimensional Chromium Selenides.

Emerging 2D chromium-based dichalcogenides (CrXn (X = S, Se, Te; 0 < n ≤ 2)) have provoked enormous interests due to their abundant structures, intriguing electronic and magnetic properties, excellent environmental stability, and great application potentials in next generation electronics and spintronics devices. Achieving stoichiometry-controlled synthesis of 2D CrXn is of paramount significance for such envisioned investigations. Herein, we report the stoichiometry-controlled syntheses of 2D chromium selenide (CrxSey) materials (rhombohedral Cr2Se3 and monoclinic Cr3Se4) via a Cr-self-intercalation route by designing two typical chemical vapor deposition (CVD) strategies. We have also clarified the different growth mechanisms, distinct chemical compositions, and crystal structures of the two type materials. Intriguingly, we reveal that the ultrathin Cr2Se3 nanosheets exhibit a metallic feature, while the Cr3Se4 nanosheets present a transition from p-type semiconductor to metal upon increasing the flake thickness. Moreover, we have also uncovered the ferromagnetic properties of 2D Cr2Se3 and Cr3Se4 below ∼70 K and ∼270 K, respectively. Briefly, this research should promote the stoichiometric-ratio controllable syntheses of 2D magnetic materials, and the property explorations toward next generation spintronics and magneto-optoelectronics related applications.

Engineering Magnetic Soft and Reconfigurable Robots.

Magnetic control has gained popularity recently due to its ability to enhance soft robots with reconfigurability and untethered maneuverability, among other capabilities. Several advancements in the fabrication and application of reconfigurable magnetic soft robots have been reported. This review summarizes novel fabrication techniques for designing magnetic soft robots, including chemical and physical methods. Mechanisms of reconfigurability and deformation properties are discussed in detail. The maneuverability of magnetic soft robots is then briefly discussed. Finally, the present challenges and possible future work in designing reconfigurable magnetic soft robots for biomedical applications are identified.

Temperature-Dependent Modulation of Short-Wave-Infrared Light Transparency Based on Associated Structures of a Liquescent Nickel(III) Complex.

A liquescent bis(malononitriledithiolato)nickel(III) complex with a bis(methoxyethyl)imidazolium cation, 1[Ni(mnt)2 ], exhibits three-stage thermochromic modulation of transparency/absorption in the short-wave-infrared (SWIR) region (1000-2500 nm), driven by associated structural changes. Upon heating, the electronic spectra of 1[Ni(mnt)2 ] in the SWIR region shift to shorter wavelengths accompanying with the solid-liquid phase transition at 76 °C. Further heating to over 109 °C induces a second transition of the electronic spectra, characterized by a blue-shift of the SWIR absorption in the liquid phase. The results of temperature-dependent electronic spectra and magnetic susceptibility indicated that the thermochromic changes can be attributed to the two-step dissociation of the associated structures of [Ni(mnt)2 ]- , occurring during the solid-liquid phase transition and the shift of dimer-monomer equilibrium in the liquid state. These changes can be visualized using an SWIR imaging camera under appropriate SWIR lights.

Tailoring Mechanical and Magnetic Properties in Dual-Phase FeCoNi(CuAl)0.8 High-Entropy Alloy.

For tailoring the mechanical and magnetic properties of dual-phase high-entropy alloys (HEAs), it is crucial to understand the effect of each phase on the overall properties. In this paper, the effects of individual FCC and BCC phases on the mechanical and magnetic properties of the FeCoNi(CuAl)0.8 HEA are investigated by nanoindentation and first-principles calculations. The nano-hardness of the BCC phase is 8.73 GPa, which is nearly double the 4.60 GPa of the FCC phase, which ascribes to spherical nanoprecipitates that are only observed in the BCC phase leading to precipitation hardening. First-principles calculations on the electronic structure show that calculated saturation magnetization (Ms) of the BCC phase is 0.81 T, higher than 0.77 T of the FCC phase. An approximate yield strength and Ms can be estimated by summing the volume-fraction-weighted contributions from each phase, and are in good agreement with experimental values. It indicates that the overall mechanical and magnetic properties of the dual-phase HEAs can be tailored by tuning the volume fraction of the individual phase. Our findings are helpful to design prospective dual-phase HEAs with both good mechanical properties and soft magnetic performance by adjusting the content of each phase.

Nanosized core-shell (NiFe2O4/TiO2) heterostructure for enhanced photodegradation against polycyclic aromatic hydrocarbons.

The global level of attention has been raised for photocatalytic pollutant removal technologies for degrading organic pollutants because of rising concerns about their toxicity. In this study, NiFe2O4/TiO2 core shells and pure samples of NiFe2O4 and TiO2 were synthesized using the sol-gel process and used to degrade naphthalene which is one among the polycyclic aromatic hydrocarbons (PAHs) pollutant. The synthesized materials were evaluated using a variety of analytical techniques, and the typical NiFe2O4/TiO2 core-shell results showed good purity and a lack of other impurity structures. Through morphological characterization, the core-shell structure of NiFe2O4/TiO2 has been established. However, the activity of visible light degradation was boosted by the generation of hydroxyl radicals after the electron-hole pair was delayed. Additionally, a lower band gap in NiFe2O4/TiO2 than in pure materials promotes photocatalytic activity. Similarly, photocatalytic naphthalene elimination by the core-shell achieved 67% efficiency after 150 min of visible light exposure. Furthermore, the produced core-shell has a high magnetic property, making separation from the photo-irradiated solutions easier; as a result, recycling was likely successful up to three cycles. The photocatalytic mechanism of the NiFe2O4/TiO2 composite was proposed. This research could also be applied to the degradation of other polycyclic aromatic hydrocarbon contaminants.

Magnetic Property, Heat Capacity and Crystal Structure of Mononuclear Compounds Based on Substitute Tetrazole Ligand.

Three mononuclear compounds formulated as {M[(2-1H-tetrazol-5-yl)pyridine]2(H2O)2} (M = FeII (1), CoII (2), CuII (3)) were reported and synthesized. Their space group is monoclinic, P21/c, revealed by single-crystal X-ray diffraction. Antiferromagnetic interactions exist in Compounds 1, 2 and 3, as evidenced by magnetic and low-temperature heat capacity measurements. In addition, their thermodynamic functions were determined by a relaxation calorimeter, indicating that Compound 1 exhibits a Schottky anomaly in low-temperature heat capacity. This work can provide an important fundamental basis for the research of the thermophysical properties of molecular-based magnetic materials.

Preparation, phase stability, and magnetization behavior of high entropy hexaferrites.

The polycrystalline SrFe12O19 samples deeply substituted up to at.67% by Al3+, Ga3+, In3+, Co3+, and Cr3+ cations with a high configurational mixing entropy were prepared by solid-phase synthesis. Phase purity and unit cell parameters were obtained from XRD and analyzed versus the average ionic radius of the iron sublattice. The crystallite size varied around ∼4.5 µm. A comprehensive study of the magnetization was realized in various fields and temperatures. The saturation magnetization was calculated using the Law of Approach to Saturation. The accompanying magnetic parameters were determined. The magnetic crystallographic anisotropy coefficient and the anisotropy field were calculated. All investigated magnetization curves turned out to be nonmonotonic. The magnetic ordering and freezing temperatures were extracted from the ZFC and FC curves. The average size of magnetic clusters varied around ∼350 nm. The high values of the configurational mixing entropy and the phenomenon of magnetic dilution were taken into account.

Magnetic behavior of Fe3O4@C nanofibers by a facile co-axial electrospinning method.

Co-axially electrospun, magnetic Fe3O4@carbon (Fe3O4@C) nanofibers comprising Fe3O4particles in the core and carbon in the shell have been fabricated and their performances as magnetic material have been studied. The electrospun Fe3O4@C nanofibers have been characterized with x-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscope, x-ray photoelectron spectroscope (XPS), and superconducting quantum interference device magnetometer. The structural and microstructural analysis has given a brief idea about the pure Fe3O4and C phase formation and also the existence of smooth and continuous morphology of Fe3O4@C nanofibers. It has been shown that there exist two different oxidation states of Fe in the XPS spectrum. The magnetization hysteresis loop has been observed at low temperatures (5 K, 100 K) as well as at room temperature (300 K) which gives different magnetic parameters. Temperature dependent magnetic measurements (from 5 to 300 K) suggest the existence of Verwey transition for lower percentage of iron oxide content.

Test and Analysis of High-Permeability Material's Microstructure in Magnetic Shielding Device.

The magnetic shielding device is used to provide an extreme weak magnetic field, which plays a key role in variety of fields. Since the high-permeability material constituting the magnetic shielding device determines the magnetic shielding performance, it is important to evaluate the property of the high-permeability material. In this paper, the relationship between the microstructure and the magnetic properties of the high-permeability material is analyzed using minimum free energy principle based on magnetic domain theory, and the test method of the material's microstructure including the material composition, the texture and the grain structure to reflect the magnetic properties is put forward. The test result shows that the grain structure is closely related to the initial permeability and the coercivity, which is highly consistent with the theory. As a result, it provides a more efficient way to evaluate the property of the high-permeability material. The test method proposed in the paper has important significance in the high efficiency sampling inspection of the high-permeability material.

Magnetic properties induced by the Yb-valence inhomogeneity in the layered Kondo-lattice compound Yb4RuGe8.

We have successfully grown single crystals of a novel ytterbium-based layered compoundYb4RuGe8and studied its structural, magnetic, thermal, and transport properties. The magnetic susceptibility has a broad peak caused by the Kondo effect at approximately40 Kand is enhanced below15 Kowing to the development of additional magnetic correlations. An analysis with the grand-Kadowaki-Woods relation reveals that the low-temperature state except for the effect of the additional magnetic correlations is a heavy-mass Fermi liquid.

Manipulating Electron-Transfer Events in [Fe4 Co4 ] Cubes via a Mixed-Ligand Approach: The Impact of Elastic Frustration.

The engineering of intermolecular interaction is challenging but critical for magnetically switchable molecules. Here, we prepared two cyanide-bridged [Fe4 Co4 ] cube complexes via the alkynyl- and alcohol-functionalized trispyrazoyl capping ligands. The alkynyl-functionalized complex 1 exhibited a thermally-induced incomplete metal-to-metal electron transfer (MMET) behaviour at around 220 K, while the mixed alkynyl/alcohol-functionalized cube of 2 showed a complete and abrupt MMET behaviour at 232 K. Remarkably, both compounds showed a long-lived photo-induced metastable state up to 200 K. The crystallographic study demonstrated that the incomplete transition of 1 was likely due to the possible elastic frustration originating from the competition between the anion-propagated elastic interactions and inter-cluster alkynyl-alkynyl & CH-alkynyl interactions, whereas the latter are eliminated in 2 as a result of the partial substitution by the alcohol-functionalized ligand. Additionally, the introduction of chemically distinguishable cobalt centers within the cube unit of 2 did not lead to a two-step but a one-step transition, possibly because of the strong ferroelastic intramolecular interaction through the cyanide bridges.

Advances in Two-Dimensional Magnetic Semiconductors via Substitutional Doping of Transition Metal Dichalcogenides.

Transition metal dichalcogenides (TMDs) are two-dimensional (2D) materials with remarkable electrical, optical, and chemical properties. One promising strategy to tailor the properties of TMDs is to create alloys through a dopant-induced modification. Dopants can introduce additional states within the bandgap of TMDs, leading to changes in their optical, electronic, and magnetic properties. This paper overviews chemical vapor deposition (CVD) methods to introduce dopants into TMD monolayers, and discusses the advantages, limitations, and their impacts on the structural, electrical, optical, and magnetic properties of substitutionally doped TMDs. The dopants in TMDs modify the density and type of carriers in the material, thereby influencing the optical properties of the materials. The magnetic moment and circular dichroism in magnetic TMDs are also strongly affected by doping, which enhances the magnetic signal in the material. Finally, we highlight the different doping-induced magnetic properties of TMDs, including superexchange-induced ferromagnetism and valley Zeeman shift. Overall, this review paper provides a comprehensive summary of magnetic TMDs synthesized via CVD, which can guide future research on doped TMDs for various applications, such as spintronics, optoelectronics, and magnetic memory devices.

Versatile magnetic hydrogel soft capsule microrobots for targeted delivery.

Maintaining the completeness of cargo and achieving on-demand cargo release during long navigations in complex environments of the internal human body is crucial. Herein, we report a novel design of magnetic hydrogel soft capsule microrobots, which can be physically disintegrated to release microrobot swarms and diverse cargoes with almost no loss. CaCl2 solution and magnetic powders are utilized to produce suspension droplets, which are put into sodium alginate solution to generate magnetic hydrogel membranes for enclosing microrobot swarms and cargos. Low-density rotating magnetic fields drive the microrobots. Strong gradient magnetic fields break the mechanical structure of the hydrogel shell to implement on-demand release. Under the guidance of ultrasound imaging, the microrobot is remotely controlled in acidic or alkaline environments, similar to those in the human digestion system. The proposed capsule microrobots provide a promising solution for targeted cargo delivery in the internal human body.

Magnetization controlled by crystallization in soft magnetic Fe-Si-B-P-Cu alloys.

Soft magnetic materials have low coercive fields and high permeability. Recently, nanocrystalline alloys obtained using annealing amorphous alloys have attracted much interest since nanocrystalline alloys with small grain sizes of tens of nanometers exhibit low coercive fields comparable to that of amorphous alloys. Since nanocrystalline soft magnetic materials attain remarkable soft magnetic properties by controlling the grain size, the crystal grains' microstructure has a substantial influence on the soft magnetic properties. In this research, we examined the magnetic properties of Fe-Si-B-P-Cu nanocrystalline soft magnetic alloys obtained by annealing amorphous alloys. During crystallization, the observation findings reveal the correlation between the generated microstructures and soft magnetic properties.