External Magnetization Research Articles

Boosting Li-S batteries through the synergistic effect of recycled ferrites and external magnetic induction

Despite being considered one of the most promising energy storage technologies, lithium-sulfur batteries (LSBs) are limited in terms of commercialization by the shuttle effect and slow reaction kinetics. In this work, we demonstrate for the first time that the use of recycled ferrite in conjunction with an external magnetic field generated by a permanent magnet can enhance the reaction kinetics and the adsorption of polysulfides (LiPSs), and hence the electrochemical stability. An in-depth kinetic study shows that under the effect of an external magnetic field, the electrode has lower polarization, a higher Li+ diffusion coefficient and a lower activation energy between electrochemical stages. The electrode also has a capacity retention up to 40 % higher and half the capacity loss per cycle at a high rate of 1C. At an ultra-high rate of 10C, the electrode has a capacity of 507 mAh g−1 after 150 cycles and an areal capacity of up to 3 mAh cm−2 at an ultra-high loading of 13 mg cm−2. In addition to the promising results observed in electrochemical terms, our approach is also more sustainable due to the use of a recycled electronic material obtained via dry milling, thereby avoiding the use of fossil carbons.

Thermal gradient-induced critical current degradation in mesoscopic superconducting thin film

Abstract Superconducting materials inevitably suffer from the sudden change of temperature in localized areas in practical applications, and the concomitant thermal gradient may be detrimental to their performance. Critical current density is a key factor affecting the performance of superconductors. However, the effect of thermal gradient on the critical current density has not been identified. Here, by combining the time-dependent Ginzburg–Landau equations and the heat transfer equation, the thermal gradient and magnetic field dependence of the critical current density are systematically investigated and rationalized by exploring the behavior of vortex and magnetization. For lower magnetic fields, it is found that the thermal gradients strongly reduce the local surface barriers, which inhibits vortex entry and movement, leading to a rapid deterioration of the current-carrying capability. Under moderate magnetic fields, the critical current density corresponding to higher thermal gradients decreases more slowly with increasing magnetic field, which results from the thermal gradient-induced entry and moving of vortices along the current direction. As the magnetic field continues to increase, the variation of the critical current density transitions into a platform period and even slightly rises. The enhanced critical current is primarily attributed to the excess entry of vortices, which increases the surface barrier of the sample. With the further increase in the magnetic field, the critical current density continues to decrease due to increased magnetic field penetration. These results unveil the fundamental interplay between thermal gradients, external magnetic field, vortex, magnetization and critical current density, and provide a theoretical basis for understanding the heat-induced quenching of mesoscopic superconducting thin films in practical applications.

Large out-of-plane spin–orbit torque in topological Weyl semimetal TaIrTe4

The unique electronic properties of topological quantum materials, such as protected surface states and exotic quasiparticles, can provide an out-of-plane spin-polarized current needed for external field-free magnetization switching of magnets with perpendicular magnetic anisotropy. Conventional spin–orbit torque (SOT) materials provide only an in-plane spin-polarized current, and recently explored materials with lower crystal symmetries provide very low out-of-plane spin-polarized current components, which are not suitable for energy-efficient SOT applications. Here, we demonstrate a large out-of-plane damping-like SOT at room temperature using the topological Weyl semimetal candidate TaIrTe4 with a lower crystal symmetry. We performed spin–torque ferromagnetic resonance (STFMR) and second harmonic Hall measurements on devices based on TaIrTe4/Ni80Fe20 heterostructures and observed a large out-of-plane damping-like SOT efficiency. The out-of-plane spin Hall conductivity is estimated to be (4.05 ± 0.23)×104 (ℏ ⁄ 2e) (Ωm)−1, which is an order of magnitude higher than the reported values in other materials.

Minimization of a ship's magnetic signature under external field conditions using a multi-dipole model

The paper addresses the innovative issue of minimizing the ship's magnetic signature under any external field conditions, i.e., for arbitrary values of ambient field modulus and magnetic inclination. Varying values of the external field, depending on the current geographical location, affect only the induced part of ship's magnetization. A practical problem in minimizing the ship signature is separating permanent magnetization from induced magnetization. When the ship position changes, a signature measurement has to be made under new magnetic field conditions to update the currents in the coils. This is impractical or even difficult to do (due to the need for a measuring ground), so there is a need to predict the ship's magnetization value in arbitrary geographical location conditions based on the reference signature determined on the measuring ground. In particular, the model predicting the signatures at a new geographical location must be able to separate the two types of magnetization, as permanent magnetization is independent of external conditions. In this paper, a FEM model of the vessel is first embedded in an external field and permanent magnetization is simulated using DC coils placed inside the model. Then, using the previously developed rules for data acquisition and determination of model parameters, a multi-dipole model is synthesized in which the induced and permanent parts are separated. The multi-dipole model thus developed has been successfully confronted with the initial model in FEM environment. The separation of permanent and induced magnetization allows the latter to be scaled according to new values of the external field. In the paper, the situation of determining a signature at one geographical position and its projection onto two other positions is analyzed. Having determined the signature with a high degree of accuracy anywhere in the world, it is possible to perform classical signature minimization by determining DC currents in coils placed inside the ship's hull. The paper also analyzes the effectiveness of ship's signature minimization and the influence of ship's course on the signature value. The advantage of the method presented in this paper is an integrated approach to the issue of scaling and minimization of ship magnetic signature, which has not been presented in the literature on such a scale before.

Триплеттриплетная аннигиляция молекулярных электронных возбуждений вблизи диамагнитной металлической микрочастицы в переменном магнитном поле

A mathematical model of the spinselective reaction of triplettriplet annihilation of molecules on the surface of a spherical microparticle or a cylindrical rod of micrometer radius in an alternating magnetic field transformed by conducting microparticles is presented. Based on these models, the calculations of the integral and local rates of magnetically sensitive molecular processes were performed. It has been shown that in the local nearsurface regions of the conducting microparticles in an alternating magnetic field, the rate of spinselective bimolecular reactions changes. The comparison of the nanoand microsphere showed that with the external magnetic field induction value B0 = 1 T, the maximum resulting field at the equator of the particle was equal to 12 mT and 100 mT, respectively. It was also revealed that for nanoand microcylinders with a similar value of the external magnetic field induction B0 = 1 T, the maximum resulting field at the point (R,0) of the 2d magnetic pole was equal to 12 mT and 1.5 T, respectively. The amplitude of the magnetic effect for different times and particle sizes was equal to +1 % and 2 %. For a silver microcylinder with a radius R = 25 μm, there was switching from a purely negative magnetic effect at the time t = 0 ns to an effect with positive and negative parts. For the case of a silver cylinder of radius R = 30 μm and external magnetic field frequency ω = 5∙108 s1, an increase in the amplitude of the positive part of the magnetic effect curve from 0.25 % to 1 % was observed when the time instant changed from t = 0 ns, which corresponds to the maximum of the external magnetic field, up to t = 3.68 ns when the resulting field of the microwire reaches its maximum. This work may be of interest to physicists and chemists involved in science in the field of chemical physics, physics of magnetic phenomena, spinselective reactions and spintronics.

Verification of External Magnetization based EM Technique for Diagnosing Residual Tensile Stress in Aged PSC Structures

Verification of External Magnetization based EM Technique for Diagnosing Residual Tensile Stress in Aged PSC Structures

Theoretical studies of magneto-optical Kerr and Faraday effects in two-dimensional second-order topological insulators

Optical approaches are useful for studying the electronic and spin structure of materials. Here, based on the tight-binding model and linear response theory, we investigate the magneto-optical Kerr and Faraday effects in two-dimensional second-order topological insulators (SOTI) with external magnetization. We find that orbital-dependent Zeeman term induces band crossings for SOTI phase, which are absent for trivial phase. In the weak-magnetization regime, these crossings give rise to giant jumps (peaks) of Kerr and Faraday angles (ellipticity) for SOTI phase. In the strong-magnetization regime, we find that two nearly flat bands are formed at the high-symmetry point of Brillouin zone of SOTI phase. These flat bands give rise to two successive giant jumps (peaks) of Kerr and Faraday angles (ellipticity). These phenomena provide new possibilities to characterize and detect the two-dimensional SOTI phase.

An efficient and sustainable Pd‐nanomagnetic heterogeneous catalyst for the reduction of nitroarene and environmental pollutant

This study reports the synthesis and characterization of an environmentally friendly, cost‐effective, and sustainable Pd‐heterogeneous catalyst anchored on superparamagnetic silica‐coated iron oxide. The synthesized Pd‐SB/MNP nanomagnetic catalyst was extensively characterized using Fourier transform infrared (FTIR), inductively coupled plasma optical emission spectroscopy (ICP‐OES), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), energy‐dispersive spectrometry (EDS), vibrating sample magnetometry (VSM), field emission scanning electron microscopy (FE‐SEM), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), and high‐resolution transmission electron microscopy (HR‐TEM). The Pd‐SB/MNP catalyst showed remarkable efficiency in catalyzing the reduction of nitroarene and Cr(VI) under mild reaction conditions using an eco‐friendly solvent. The catalyst exhibits facile recovery through external magnetization, enabling its efficient recycling and reutilization for at least 10 cycles while demonstrating minimal Pd loss, as confirmed by rigorous hot filtration testing and ICP‐OES analysis. These results comply with the industry's prescribed thresholds for permissible levels of residual metallic content. The results suggest that the synthesized Pd‐SB/MNP catalyst holds great potential for various industrial applications.

Generalized method of image dyons for quasi-two dimensional slabs with ordinary - topological insulator interfaces

Electrostatic charges near the interface between topological (TI) and ordinary (OI) insulators induce magnetic fields in the medium that can be described through the so-called method of image dyons (electric charge - magnetic monopole pairs), the magnetoelectric extension of the method of image charges in classical electrostatics. Here, we provide the expressions for the image dyons and ensuing magnetoelectric potentials in a system comprised by two planar-parallel OI-TI interfaces conforming a finite-width slab. The obtained formulae extend earlier work in that they account for all different combinations of materials forming the slab and its surroundings, including asymmetric systems, as well as all possible combinations of external magnetization orientations on the interfaces. The equations are susceptible of implementation in simple computational codes, to be solved recurrently, in order to model magnetoelectric fields in topological quantum wells, thin films, or layers of two-dimensional materials. We exemplify this by calculating the magnetic fields induced by a point charge in nanometer-thick quantum wells, by means of a Mathematica code made available in repositories.

Hydromagnetic Waves in Cold Nuclear Matter

I consider a proton–neutron fluid mixture placed in an ultra-strong external static magnetic field and derive the spin-independent, small-amplitude disturbances in infinitely extended systems. As a theoretical framework I adopt a hydrodynamical model for the proton and neutron fluids moving in a Skyrme mean-field derived from the time-dependent Hartree Fock formulation of the many-body nuclear problem. From the mass, momentum balance, and Maxwell equations, I set up a system of equations governing the electromagnetic field and the continuum-mechanical fields of the mixture. Next, the hydromagnetic equations are linearized, and the occurrence of small-amplitude distortions of the velocity field is analyzed for various orientations of the constant external magnetic induction with respect to the wave propagation vector. The derivation of the above equations is carried out for the inviscid case.

Magnetic field and nuclear spin influence on the DNA synthesis rate

The rate of a chemical reaction can be sensitive to the isotope composition of the reactants, which provides also for the sensitivity of such “spin-sensitive” reactions to the external magnetic field. Here we demonstrate the effect of the external magnetic field on the enzymatic DNA synthesis together with the effect of the spin-bearing magnesium ions (^{25}Mg). The rate of DNA synthesis monotonously decreased with the external magnetic field induction increasing in presence of zero-spin magnesium ions (^{24}Mg). On the contrary, in the presence of the spin-bearing magnesium ions, the dependence of the reaction rate on the magnetic field induction was non-monotonous and possess a distinct minimum at 80–100 mT. To describe the observed effect, we suggested a chemical scheme and biophysical mechanism considering a competition between Zeeman and Fermi interactions in the external magnetic field.

Production and characterization of magnetic textiles

In this study, 100% cotton fabrics were imparted with magnetic field properties using a conventional screen printing method to obtain magnetic fabrics in the context of smart textiles. The magnetism in the fabrics was generated by using a Fe3O4 compound. In order to make this compound adhere more strongly to the fabric sample, printing method was used as a finishing application. The Fe3O4 compound was added to the printing paste without using any dyestuff since the Fe3O4 compound had a unique color itself. The washing durability of the printed functional textiles were investigated. The washing fastness, acidic sweat fastness, alkaline sweat fastness, water fastness, dry rubbing fastness, wet rubbing fastness, tear strength, pilling and degree of external magnetic induction of the fabrics were analyzed. In addition, the morphological analyzes of the fabrics were performed by scanning electron microscopy (SEM-EDX) and X-ray crystallography (XRD) to determine the crystallographic properties of the materials and the phases they contained. According to the result of quantitative evaluation of magnetic fields on textile surfaces, Fe3O4 microparticles were in the range of 25 mT when they constituted 50% of the weight.Thus, it was found that a magnetic field was successfully generated in the textiles. Moreover, the magnetic property of the fabric was durable after the washing process as the mT values were maintained even after 20 washing cycles, and the fastness and performance tests were also at the highest level. Increasing the Fe3O4 content in the formulations used in the study improved the tensile strength by 2-7%. Comparing the test results of the fabric sample with the optimum formulation with the untreated fabric sample, it was also determined that the tensile strength increased by 8-10% on average after 20 washes.

Enhanced spin–orbit torque efficiency with low resistivity in perpendicularly magnetized heterostructures consisting of Si-alloyed β-W layers

Spin-orbit torque (SOT) based magnetization switching is of current technological interest to demonstrate its utilization in nonvolatile embedded memory and logic devices. These devices require perpendicular magnetic anisotropy (PMA) for high bit density, significant SOT efficiency to warrant low power consumption, and external field-free magnetization switching. Above all, materials associated with these devices must be semiconductor fabrication friendly. However, only a few materials and their heterostructures previously explored fulfill the requirements. Here, we propose a W–Si alloy, a widely used material in semiconductor devices, as the spin current-generating layer. First, we investigate the spin Hall conductivity of W–Si alloys by adding Si atoms to the β-W matrix using the first-principles calculations. Then, experimentally, we confirm that the heterostructure consisting of W-Si (4 at%)/CoFeB exhibits PMA, a high damping-like SOT efficiency (∼0.58), and low longitudinal resistivity (∼135 μΩ cm). Furthermore, we estimate ten times smaller write power consumption than the heterostructure based on the pristine β-W. The proposed W–Si/CoFeB heterostructures can withstand post-deposition heat treatment up to 500 °C.

Laser-Induced Magnetization Dynamics in Si-Doped Yttrium-Iron Garnet Film

We experimentally demonstrate that the excitation of a silicon-doped yttrium-iron garnet film by femtosecond laser pulses triggers a magnetization precession with an amplitude determined by the external magnetization direction. The maximum efficiency is achieved at the pump wavelength corresponding to the absorption maximum due to doping with silicon ions. Based on the azimuthal dependences of the precession amplitude and frequency, it is shown that the magnetization dynamics is induced by a thermal disruption of the magnetocrystalline anisotropy. By modeling hysteresis loops, it was found that the silicon doping leads to a decrease in the value of the exchange interaction in the film and an increase in the anisotropy field.

Higher Chern number states in curved periodic nanowires

The coupling between the spin and momentum degrees of freedom due to spin–orbit interactions (SOI) suggests that the strength of the latter can be modified by controlling the motion of the charge carriers. In this paper, we investigate how the effective SOI can be modulated by constraining the motion of charge carriers to curved waveguides thereby introducing real-space geometric curvature in their motion. The change in the SOI can in turn induce topological phase transitions in the system. Specifically, we study how the introduction of periodic sinusoidal curvature in nanowires with intrinsic SOC can induce the onset of mid-gap topologically protected edge states, which can be characterized by a topological invariant or Chern number. The Chern number corresponds to the number of discrete charges that would be pumped across the length of the nanowire when the phase of a sliding gate potential relative to that of the sinusoidal curvature is varied adiabatically over a complete period. In addition, coupling to an external magnetization can be utilized as an experimental knob to modify the Chern number by displacing the energies of the curvature-induced bands relative to one another. The magnetization can be tuned to achieve large discrete jumps in the number of pump charges per phase period.

Increasing power of generator on nonlinear magnetic nanostructure

Background: One of the most promising areas of development of modern electronics is the creation of spintronic devices, which should replace the traditional semiconductor elements. The use of electron spin as a carrier of information in magnetic nanostructures can radically change modern life. Objectives: The aim of this work is to find ways to increase the power of the generator on the magnetic nanostructure by changing its electrical circuit and more optimal external electromagnetic parameters that affect the state of electrons in the studied layered structure. Materials and methods: The solution of this problem is carried out by numerical simulation of the magnetic nanostructure using a specially created micromagnetic simulator, which implements an algorithm for the simultaneous solution of the system of Maxwell and Landau-Lifshitz-Hilbert equations. The solution of such a complex problem is accelerated by the use of a quasi-static approximation in solving the system of Maxwell's equations, which is justified by the small size of the calculation area compared to the depth of the skin layer. Further calculations of the electrodynamic system are performed using the finite element method. To obtain the best frequency and energy parameters of the generator, it is proposed to introduce a resonant circuit to the schematic diagram of the studied generator, which is excited by short nanosecond pulses. Results: A scheme of a generator on a magnetic nanostructure containing a resonator with concentrated parameters is proposed, and a system of nonlinear integro-differential equations with respect to electric currents is obtained in general. Numerical calculation of this system includes, in addition to the calculation of the scheme, also the modeling of a nonlinear electrodynamic structure by the finite element method. The energy and spectral characteristics of the studied generator are obtained. The search for the optimal values of the geometric parameters of the nanostructure and the magnitude of the external longitudinal magnetization is carried out. Conclusions: Due to the complex nature of nonlinear processes in the magnetic nanostructure, the use of an external resonator, which could improve the spectral parameters of the generated current, did not give a noticeable improvement. The influence of the value of the external magnetization on the output power of the generator is complex and nonlinear, but, in general, a decrease in the level of magnetization leads to a significant decrease in power. It is established that the thickness of the magnetic layer of 6 nm is optimal for improving the energy characteristics of the generator.

Pauli paramagnetism of triplet Cooper pairs in a nematic superconductor

We investigate the response of a doped topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ with spin-triplet nematic superconductivity to external magnetization. We calculate the Zeeman part of the magnetic susceptibility for nematic and chiral superconducting phases near ${T}_{c}$ in the Ginzburg-Landau formalism. The superconducting order parameter from the ${E}_{u}$ representation has nontrivial coupling with the transversal Zeeman field that results in a paramagnetic response to magnetization. The topology of a Fermi surface has a strong influence on magnetic susceptibility. The Lifshitz transition from a closed to open Fermi surface eventually leads to a phase transition from the nematic to chiral phase. At the transition point, magnetic susceptibility diverges. Also, we study the effects of the electron-electron interaction on the competition between nematic and chiral phases. We find that in a real system, electron-electron interaction can drive the nematic to chiral phase only in the vicinity of the phase transition. We compare our results with the existing experimental data.

Preparation of Fe3O4/Ag3VO4/Au nanocomposite coated with Caerophyllum macropodum extract modified with oleic acid for theranostics agent in medical imaging

Today, theranostics is one of the most important research areas in medicine. They have a special focus on the simultaneous use of an agent for diagnosis and treatment. This study aimed to synthesize a multifactorial nanocomposite consisting of Fe3O4/Ag3VO4/Au three-component coated with C. macropodum extract modified with oleic acid for theranostics and conjugated with methotrexate. In the method, the effect of coating and modified fatty acid was investigated in the design of nanoparticles. The C. macropodum extract improves the effect of methotrexate. Also, C. macropodum extract in high temperature decomposes. Oleic acid increases its stability and does not allow it to decompose soon. The final sample was confirmed by MTT, MRI, and CT scanning. VSM results showed that the resulting nanocomposite has good magnetic properties for MRI, CT, and methotrexate delivery under external magnetic field induction. Biocompatibility and cytotoxicity of nanocomposites use the MTT method, the results clearly showed its non-toxicity. The conclusion of different tests indicated that the new design is very suitable for process CT scanning and MRI.

Numerical Model of Eddy Current Inspection with DC Magnetic Field Associated

Most non-destructive techniques can be well represented in a virtual environment, in particular, eddy current testing (ECT) simulation is a useful and well-established tool to predict and represent real inspection situations permitting testing customization in a fast, cheap and efficient way. Conventional ECT generally works with low-intensity magnetic fields, however, for advanced variations of the technique, where external DC magnetic fields can be applied to locally decrease the magnetic permeability, there is no Finite Element Method (FEM) packages available to deal with such nonstandard model. Many authors [1] and [2] have presented this ECT solution for different industrial applications using external DC magnetization to carry nonlinear ferromagnetic materials to the saturation level of the magnetization curve to increase the ECT depth penetration. In general, ECT modelling calculation is benefited by properties of steady-state regime where all magnetic fields are oscillating at the same frequency not permitting through multi-frequency calculation. The present work proposes a simulation solution for such a case where DC magnetic field is associated with ECT. A theoretical model is presented together with experimental results validation.

Double-logarithmic nonlinear electrodynamics

A new model of nonlinear electrodynamics is introduced and investigated. The theory carries one dimensionful parameter β as in Born-Infeld electrodynamics. It is shown that the dual symmetry and dilatation (scale) symmetry are broken in the proposed model. The electric field of a point-like charge is derived for this model, showing that it is non-singular at the origin. Using this electric field, the static electric energy of a point-like charge is calculated. In the presence of an external magnetic field, the theory shows a phenomenon known as vacuum birefringence. The refraction index of two polarizations, parallel and perpendicular to the external magnetic induction field, are calculated. The canonical and symmetrical Belinfante energy-momentum tensors are obtained. Using the causality and unitarity principles, the regions where the theory becomes causal and unitary are found.