Influence Of External Magnetic Field Research Articles

The research on triple-coil inductive debris sensor with electromagnetic shielding

A high sensitivity inductive debris sensor is of great significance for oil condition monitoring and the fault diagnosis of mechanical equipment. However, inductive sensors are susceptible to interference from external electromagnetic fields. In this study, an inductive debris sensor with a shielding layer is studied, which can effectively reduce the influence of external magnetic fields on the sensor. Theoretical and experimental results verify the effectiveness of the shielding layer, and also show that the shielding layer impacts the magnetic field of the sensor, resulting in a decrease in the amplitude of the output signal. Detailed analysis was conducted to investigate the effect of structural parameters on the performance of inductive sensors. These parameters include the distance between the shielding layer and the coils, the thickness of the shielding layer, and the shielding layer material. Based on the theoretical and experimental results, reference suggestions are provided for the design of the shielding layer. This study ensures the performance and reliability of inductive sensors in practical applications.

Magnetic Microrobot Swarms with Polymeric Hands Catching Bacteria and Microplastics in Water.

The forefront of micro- and nanorobot research involves the development of smart swimming micromachines emulating the complexity of natural systems, such as the swarming and collective behaviors typically observed in animals and microorganisms, for efficient task execution. This study introduces magnetically controlled microrobots that possess polymeric sequestrant "hands" decorating a magnetic core. Under the influence of external magnetic fields, the functionalized magnetic beads dynamically self-assemble from individual microparticles into well-defined rotating planes of diverse dimensions, allowing modulation of their propulsion speed, and exhibiting a collective motion. These mobile microrobotic swarms can actively capture free-swimming bacteria and dispersed microplastics "on-the-fly", thereby cleaning aquatic environments. Unlike conventional methods, these microrobots can be collected from the complex media and can release the captured contaminants in a second vessel in a controllable manner, that is, using ultrasound, offering a sustainable solution for repeated use in decontamination processes. Additionally, the residual water is subjected to UV irradiation to eliminate any remaining bacteria, providing a comprehensive cleaning solution. In summary, this study shows a swarming microrobot design for water decontamination processes.

Influence of external magnetic field on intraband transitions in lens-shaped quantum dot

Intraband linear and nonlinear optical absorption in a strongly oblate lens-shaped Ge/Si quantum dot in the presence of an axial magnetic field was theoretically studied. Quantum transitions are considered in the heavy hole subband, when the scalar effective mass approximation is correct. The linear and nonlinear absorption coefficients, refractive index changes and the second harmonic generation coefficient were determined. The influence of the effects of temperature, size quantization and magnetic field on the behavior of the above parameters was revealed.

A Numerical Study on the Influence of External Magnetic field on Hydrogen Electric Arc Flow

We present a 3D numerical model capable of simulating hydrogen electric arc. The numerical model couples the electromagnetic field with hydrogen plasma arc dynamics (flow and heat transfer). Electric arc operates under the conditions of atmospheric pressure using direct current (DC) in the presence of external magnetic field. It is found that arc instabilities emerge spontaneously near the cathode before propagating downwards along the arc jet. Also, spontaneous splitting into several arcs is observed before merging again into one arc. The horizontal magnetic field induces arc skewing and directional flow perpendicular to the applied magnetic field. However, the axial magnetic field induces a rotational flow and arc swirling.

Mathematical model of weakly coupled spherical resonator chains under the influence of external magnetic field

Mathematical model of weakly coupled spherical resonator chains under the influence of external magnetic field

Thickness- and Field-Dependent Magnetic Domain Evolution in van der Waals Fe3GaTe2.

The discovery of room-temperature ferromagnetism in van der Waals (vdW) materials opens new avenues for exploring low-dimensional magnetism and its applications in spintronics. Recently, the observation of the room-temperature topological Hall effect in the vdW ferromagnet Fe3GaTe2 suggests the possible existence of room-temperature skyrmions, yet skyrmions have not been directly observed. In this study, real-space imaging was employed to investigate the domain evolution of the labyrinth and skyrmion structure. First, Néel-type skyrmions can be created at room temperature. In addition, the influence of flake thickness and external magnetic field (during field cooling) on both labyrinth domains and the skyrmion lattice is unveiled. Due to the competition between magnetic anisotropy and dipole interactions, the specimen thickness significantly influences the density of skyrmions. These findings demonstrate that Fe3GaTe2 can host room-temperature skyrmions of various sizes, opening up avenues for further study of magnetic topological textures at room temperature.

Electromagnetically induced transparency in a quantum ring: Interband transition

In this paper, we study the electromagnetically induced transparency (EIT) of a quantum ring by considering both interband and intraband transitions, under the influence of external electric and magnetic fields, as well as Rashba spin–orbit interaction (RSOI). Four band k⋅p model along with effective mass one band approximation were respectively employed to compute valence and conduction bands energy eigenvalues. We investigate the effects of applied electric and magnetic fields, as well as RSOI and the ring dimensions, on EIT. Our results reveal that the external magnetic field and the ring dimensions have a great influence on the EIT phenomenon. Ultimately, our numerical results will be used to develop devices with controllable nonlinear optical absorption and refraction.

On the magnetization of an antiferromagnetic film with uniaxial magnetocrystalline anisotropy

In this work finite element micromagnetic simulations were performed in order to study the magnetic behavior of an antiferromagnetic film with uniaxial magnetocrystalline anisotropy under the influence of external magnetic fields. The stability of the antiferromagnetic phase and metamagnetic phases arising from it, as well as the features and the evolution of the magnetic microstructure are studied in three different combinations of the easy axis and applied field directions. The investigation was carried out in a wide range of geometrical and intrinsic film’s parameters in order to derive analytical relations regarding the critical external fields.

Исследование изменения геометрических параметров образцов, наплавленных методом GMAW при воздействии на электрическую дугу продольного магнитного поля

Introduction. The paper presents the results of research of additive manufacturing process by electric arc with axial feeding of steel filler wire in protective gas environment (GMAW technology) with additional influence of external longitudinal magnetic field on electric arc. Purpose of work: an experimental study of the effect of a longitudinal magnetic field during additive manufacturing by an electric arc with axial feed of filler wire made of structural steels in a protective gas environment on the change in the geometrical characteristics of the layers being surfaced. Research Methods. The manufacturing of specimens was carried out on a 5-axis additive machine based on a CNC machine. Surfacing was carried out in the following modes: voltage 17.5 V; current 55–65 A; wire diameter 1.2 mm; wire material Sv-08G2S; wire feed rate 2,267 mm/min; approximate roll diameter 3.0 mm; roll length 50 mm; number of wires per one roll 312.5 mm; number of layers when surfacing the wall 5; magnet operation mode: alternating current with frequency 50 Hz, voltage 30 V; measured magnetic induction 5.7 mTl; initial height of the magnet above the substrate 10 mm; electrode stickout 10 mm; shielding gas: welding mixture CO2-Ar; gas pressure (flow rate) 0.15 MPa. Results and discussion. The conducted experimental study showed that the effect of longitudinal magnetic field had a statistically significant effect on the change in the dimensions of the singular, namely an increase in the width of the layers being surfaced by 34.1 %, with a calculated significance index close to zero, and a decrease in height by 20.2 %, with a calculated significance index equal to 2.7105. The effect of longitudinal magnetic field had a statistically significant effect on the change of the overall dimensions of the specimens consisting of five layers, namely, the width of the specimens increased by 11.2 % with a calculated significance index of 4.3103, and the height of the specimens decreased by 10.3 % with a calculated significance index of 6.3105. The effect of longitudinal magnetic field had no statistically significant effect on the change of the vertical deviation from straightness for the side walls of the specimens, with a calculated significance index of 0.3277, and had no statistically significant effect on the change of the error of the width of the walls of the specimens, with a significance index of 0.098.

One-step synthesis of TiO2/Fe3O4/C hydrophilic magnetic nanocomposites using the magnetized submerged arc discharge method

This study investigates the production of TiO2/Fe3O4/C hydrophilic magnetic nanocomposites produced via a one-step novel method using the submerged arc discharge method applied in liquid media of ethanol and ethanol–ammonia under the influence of external magnetic field. The magnetized submerged arc discharge forms a longer-lasting plasma arc, thereby affecting the growth of spherical and tubular carbon nanocomposites. More reactive species enrolled in the carbon growth in the magnetized submerged arc discharge, resulting in the ordered crystalline structure. The nanocomposites synthesized in ethanol–ammonia show hydrophilic characteristics, indicated by their dispersion improvement in the water and the presence of the vibrations of hydroxyl, amine, and –CN functional groups in Fourier transfer infrared (FTIR) spectra. The preparation technique described in this study using magnetized submerged arc discharge is supposed to be a simple and less costly preparation method that can potentially be further applied to produce numerous other nanocomposites.

Experimental evidences of the direct influence of external magnetic fields on the mechanism of the electrocatalytic oxygen evolution reaction

The use of magnetic fields as external stimuli to improve the kinetics of electrochemical reactions is attracting substantial attention, given their potential to reduce energy losses. Despite recent reports showing a positive effect on catalytic performance upon applying a magnetic field to a working electrode, there are still many uncertainties and a lack of experimental evidence correlating the presence of the magnetic field to the electrocatalytic performance. Here, we present a combination of electrochemical and spectroscopic tools that demonstrate how the presence of an external magnetic field alters the reaction mechanism of the electrocatalytic oxygen evolution reaction (OER), accelerating the overall performance of a Ni4FeOx electrode. Complementary experimental evidence has been gathered supporting the participation of this microscopic magnetic field effect. Electrochemical impedance spectroscopy (EIS) points to a speed-up of the intrinsic reaction kinetics, independent of other indirect effects. In the same direction, the spectro-electrochemical fingerprint of the intermediate species that appear during the electrocatalytic cycle, as detected under operando conditions, indicates a change in the order of the reaction as a function of hole accumulation. All these experimental data confirm the direct influence of an external magnetic field on the reaction mechanism at the origin of the magnetically enhanced electrocatalytic OER.

Exploring approximate analytical expression for magnetic skyrmion structure based on symbolic regression method

Magnetic skyrmion is a kind of nontrivial topological magnetic structure, which can exist stably in chiral magnet with Dzyaloshinskii-Moriya (DM) interaction, and its static and dynamic properties are closely related to its structural characteristics. However, there are no general analytical expressions for skyrmion profiles. Therefore, many researchers have provided approximate solutions. In this paper, a new approach to exploring magnetic skyrmion structures is introduced by using a symbolic regression approach. Considering the influence of DM interaction and external magnetic field on magnetic skyrmion structure, two suitable approximate expressions are obtained through symbolic regression algorithms. The applicability of these expressions depends on the dominant interaction. The research results in this work validate the powerful capability of symbolic regression algorithms in exploring the magnetic skyrmion profiles. So, the present study provides a new method for finding the analytical expressions for magnetic structure.

A Semi-Empirical Model of Cathodic Arc Spot Motion under the Influence of External Magnetic Fields

Plasma generation by cathodic arc spots plays a crucial role for coating processes that make use of the Arc-PVD technology. Usually, the arc spot motion over the cathode is steered by a magnetic field of a particular distribution and magnitude to ensure a continuous plasma generation, the avoidance of liquid droplets, and a proper utilization of cathode material by homogeneous erosion. This study presents a semi-empirical model that allows for an examination and characterization of the arc spot motion with regard to direction and speed as a function of an imposed magnetic field. This model considers the different components of random walk, retrograde, and Robson drift motion. Introduced empirical coefficients were determined by corresponding experimental investigations. The calibrated model describes the arc spot motion in good agreement to the recorded spot tracks and can therefore be applied for an evaluation of different magnetic field configurations.

Linear and nonlinear electric and magneto-optical absorption coefficients and relative refractive index changes in WxMo1−xS2 monolayer: Role of tungsten contents

In this work, we study the electric and magneto-optical absorption coefficients (ACs) and relative refractive index changes (RRICs) in W[Formula: see text]Mo[Formula: see text]S2 ternary alloys under the control of tungsten contents using the compact density matrix approach. With the influence of external electric and magnetic fields, the results show that there are a series of resonant peaks for both intra-band and inter-band transitions. With an increase in W-concentration and electric and magnetic fields, the resonant peaks give a blue (red) shift and reduce (increase) their amplitudes. These results suggest a potential application of monolayer W[Formula: see text]Mo[Formula: see text]S2 in future nanoscale electronic and magneto-optical devices.

Tuning domain wall oscillation frequency in bent nanowires through a mechanical analogy

In this work, we present a theoretical model for domain wall (DW) oscillations in a curved magnetic nanowire with a constant curvature under the action of a uniaxial magnetic field. Our results show that the DW dynamics can be described as that of the mechanical pendulum, and both the NW curvature and the external magnetic field influence its oscillatory frequency. A comparison between our theoretical approach and experimental data in the literature shows an excellent agreement. The results presented here can be used to design devices demanding the proper control of the DW oscillatory motion in NWs.

Influences of External Magnetic Field on Thermo-Mechanical Vibration Analysis of Nanocomposite Beam using Higher-Order Strain Gradient Theory

Composite nanobeams with carbon nanotube (CNT) reinforcement are crucial components in various applications due to their unique mechanical and thermal properties. The present work investigates the frequency–aspect ratio relationship in composite nanobeams with CNT reinforcement, particularly under varying temperatures, magnetic field strengths, and Winkler elastic stiffnesses. The non-dimensional frequency variation with aspect ratio, influenced by temperature differences, reveals distinct behavior patterns. The introduction of a magnetic field alters frequency characteristics, with uniform distribution (UD) nanobeams displaying higher frequencies. The impact of Winkler elastic stiffness, temperature differences, and magnetic field strengths on frequency elucidates differing responses between UD, [Formula: see text]-type distribution (XD), and [Formula: see text]-type distribution (VD) nanobeams. Nonlocal strain gradient theory proves essential in capturing dynamic characteristics influenced by CNT distribution. These findings shed light on the intricate dynamics of composite nanobeams, providing valuable insights for the design of future nano-devices employing CNT-reinforced composite beams as fundamental elements.

Influence of magnetic field on the electronic ferroelectricity in the extended Falicov-Kimball model

The density-matrix-renormalization-group method is used to study the influence of external magnetic field on the stability of the excitonic phase induced by local hybridization in the one-dimensional spin-1/2 Falicov-Kimball model. It is shown that a fine tuning of external magnetic field through the quantum critical point is able to induce significant changes (continuous as well as discontinuous) in the excitonic expectation average providing new set of physical properties and technological applications, like possibilities of faster switching ferroelectrics and controlling their optical properties with magnetic fields. Moreover, effects of some other interactions (which may be present in real d-f materials) on the stability of excitonic phase are examined and it is shown that the Hubbard interaction in the d-electron subsystem, the interband d-f Coulomb interaction, as well as the exchange d-f interaction stabilize significantly excitonic correlations below the quantum critical point, while the anisotropic spin-dependent interaction of the Ising type between f and d electrons as well as the f-electron hopping suppress the excitonic correlations for magnetic fields below as well as above the quantum critical point.

Unveiling the Role of the Properties of Magnetic Nanoparticles for Highly Efficient Low-Frequency Magneto-Mechanical Actuation of Biomolecules.

The role of the properties of magnetic nanoparticles in the remote magneto-mechanical actuation of biomolecules under the influence of external magnetic fields is still of particular interest. Here, a specially designed strategy based on the mechanical destruction of short oligonucleotide duplexes is used to demonstrate the effect of magnetic nanoparticles with different sizes (5-99 nm) on the magnitude of the magneto-mechanical actuations in a low-frequency alternating magnetic field. The results show that the mechanical destruction of complementary chains of duplexes, caused by the rotational-vibrational movements of nanoparticles upon exposure to a magnetic field, has a nonmonotonic dependence on the nanoparticle core size. The main hypothesis of this phenomenon is associated with a key role of magneto-dipole interactions between individual nanoparticles, which blocks the movements of nanoparticles in dense clusters. This result will allow fine-tuning of the magnetic nanoparticle properties for addressing specific magneto-mechanical tasks.

A modified decomposition method for the analysis of porous triangular fin with a power exponent of thermal properties and magnetic effect

A closed-form solution of the triangular porous fin with a simultaneous variation of power law-dependent heat transfer coefficient, internal heat generation, and surface emissivity parameters under the influence of external magnetic and electric fields is carried out. Darcy’s model has been used to simulate flow in the porous triangular fin with insulated boundary conditions. The governing singular value equation is nondimensionalized and solved by modified Adomian decomposition method (MADM) and the results of MADM are compared with the numerical solution obtained from the finite difference method (FDM) in the limiting conditions. The graphical analysis of the significant power law variation of thermophysical parameters, Hartmann number and important design parameters such as the half-thickness parameter of the triangular fin are performed and physically interpreted. A comparative study has been carried out with multiple power law parameters at different values while other thermophysical parameters were kept at a fixed level and it has been found that fin temperature is highest at higher values of power index parameters. From this study, it has been found that with the increasing value of the Hartmann number as well as the porosity parameter, the efficiency of the triangular porous fin increases rapidly.

Influence of External Magnetic Field on 3D Thermocapillary Convective Flow in Various Thin Annular Pools Filled with Silicon Melt

Thermocapillary convection flows can have an impact on the homogeneity of floating zone semiconductor crystals. An external magnetic field can also help to reduce this non-homogeneity. The goal of this research is to minimize thermocapillary convection in various thin annular pools filled with silicon melt. A three-dimensional (3D) numerical technique is proposed that employs an implicit finite volume formulation. The steady-state thermocapillary flow in six thin annular pools (R=0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) subjected to an externally induced magnetic field was observed. Under magnetic field influence, the effects of increasing annular gap, R on the hydrothermal wave number and azimuthal pattern are obtained. The results reveal that hydrothermal waves m=14, m=11, m=8, m=6, m=4, and m=3 are observed in steady flow for R=0.3; 0.4; 0.5; 0.6; 0.7, and R=0.8, respectively. The maximum temperature occurs in the intermediate zone between the inner and outer walls when there is no magnetic field. Under a strong enough magnetic field, isothermal lines change form and become concentric circles. As the amplitude of the magnetic field (Ha) grows, the azimuthal velocity and temperature at the free surface reduce, and the asymmetric 3D flow becomes axisymmetric steady when Ha surpasses a threshold value.