Interaction Of Magnetic Field Research Articles

Kinetically blocked self-assembly of colloidal strings with tunable interactions in magnetic fields.

Tunable self-assembly driven by external electric or magnetic fields is of significant interest in modern soft matter physics. While extensively studied in two-dimensional systems, it remains insufficiently explored in three-dimensional systems. In this study, we investigated the formation of vertical strings from an initial monolayer system of particles deposited on a horizontal substrate under the influence of an external magnetic field using experiments, computer simulations, and theoretical frameworks. We demonstrated that the main mechanism of string self-assembly is merging, driven by the interplay between gravity and induced tunable interparticle interactions. During this process, the system has to overcome a saddle point on the energy landscape, whose height increases with the string height. At a certain point, further self-assembly becomes kinetically blocked in a metastable state, far from equilibrium. This contrasts sharply with the typical scenario for tunable self-assembly in two dimensions, where the resulting structures usually correspond to the equilibrium state. Therefore, this finding opens up opportunities for more detailed control of three-dimensional tunable self-assembly by designing and tuning various potential barriers along the kinetic pathways.

Su-Schrieffer-Heeger-Hubbard model at quarter filling: Effects of magnetic field and nonlocal interactions

Su-Schrieffer-Heeger-Hubbard model at quarter filling: Effects of magnetic field and nonlocal interactions

Particle-Hole Asymmetric Ferromagnetism and Spin Textures in the Triangular Hubbard-Hofstadter Model

In a lattice model subject to a perpendicular magnetic field, when the lattice constant is comparable to the magnetic length, one enters the “Hofstadter regime,” where continuum Landau levels become fractal magnetic Bloch bands. Strong mixing between bands alters the nature of the resulting quantum phases compared to the continuum limit; lattice potential, magnetic field, and Coulomb interaction must be treated on equal footing. Using determinant quantum Monte Carlo and density matrix renormalization group techniques, we study this regime numerically in the context of the Hubbard-Hofstadter model on a triangular lattice. In the field-filling phase diagram, we find a broad wedge-shaped region of ferromagnetic ground states for filling factor ν≤1, bounded below by filling factor ν=1 and bounded above by half filling the lowest Hofstadter subband. We observe signatures of SU(2) quantum Hall ferromagnetism at filling factors ν=1 and ν=3. The phases near ν=1 are particle-hole asymmetric, and we observe a rapid decrease in ground-state spin polarization consistent with the formation of skyrmions only on the electron doped side. At large fields, above the ferromagnetic wedge, we observe a low-spin metallic region with spin correlations peaked at small momenta. We argue that the phenomenology of this region likely results from exchange interaction mixing fractal Hofstadter subbands. The phase diagram derived beyond the continuum limit points to a rich landscape to explore interaction effects in magnetic Bloch bands. Published by the American Physical Society 2024

Macroscopic Room-Temperature Magnetoelectricity in Piezoelectric (Core)-Ferrimagnetic (Shell) Nanocomposites.

The magnetoelectric (ME) effect, which involves the interaction of magnetic and electric fields within a material, has a significant potential for various applications. Our study addresses the limitations of conventional magnetostriction-based ME materials by demonstrating an alternative approach that achieves substantial ME effects in core-shell-type nanocomposites at room temperature. By synthesizing ferrimagnetic Fe3O4 nanoparticles onto piezoelectric poly(vinylidene fluoride) (PVDF) particles, we identified a distinct ME mechanism. In magnetorheological (MR) fluids, the magnetic-field-induced aggregation of Fe3O4 nanoparticles, combined with the piezoelectricity of PVDF, leads to a pronounced ME effect, significantly enhancing the performance and stability of MR fluids. This research highlights a crucial observation of distinct ME effects, which could suggest potential pathways for advancements in practical applications including microfluidics, vibration dampers, tactile technologies, and biomedical and bioengineering fields.

Forgotten treasures in the HST/FOC UV imaging polarimetric archives of active galactic nuclei. III. Five years monitoring of M87

The active galactic nucleus within M87, a giant elliptical galaxy, is responsible for one of the closest kiloparsec-scale relativistic jets to Earth. It is thus a perfect target for spatially resolved observations. This one-sided jet has been extensively observed at almost all wavelengths, with almost all techniques. Among many other discoveries, it was found that the optical emission is more concentrated in the knots and along the center line of the jet, in comparison to, for example, the radio emission. A remaining question relates to what we can learn from its polarized counterpart. We unearthed unpublished polarization maps taken with the Faint Object Camera (FOC) aboard the Hubble Space Telescope (HST), obtained between 1995 and 1999. At a rate of one observation per year, we can follow the evolution of the polarized flux knots in the jet. We can thus constrain the timescale of variation in the magnetic field up to a spatial resolution of one tenth of an arcsecond (sim 11.5 pc). After coherently reducing the five observations using the same methodology presented in the first paper of this series, the analysis of polarized maps from POS 1 (base of the jet) and POS 3 (end of the jet) reveals significant temporal and spatial dynamics in the jet's magnetic field morphology. Despite minimal changes in the overall intensity structure, notable fluctuations in polarization degrees and angles are detected across various knots and inter-knot regions. In addition, the emission and polarization characteristics of M87's jet differ significantly between POS1 and POS3. POS1 shows a more collimated jet with strong variability in polarization, while POS3 reveals a thicker structure, a quasi-absence of variability, and complex magnetic field interactions. This suggests that the jet may have coaxial structures with distinct kinetic properties. Theoretical models like the jet-in-jet scenario, featuring double-helical magnetic flux ropes, help to explain these observations and indicate a strong density contrast and higher speeds in the inner jet. Our temporal analysis demonstrates the importance of high-spatial-resolution polarization mapping in understanding jets' polarization properties and overall dynamics, especially if such maps are taken at different wavelengths (ultraviolet and radio).

Effect of nanofluid cooling on electrical power of solar panel system in existence of TEG implementing magnetic force

This study investigates the efficacy of applying a Lorentz force to improve the efficiency of a photovoltaic-thermal (PVT) system featuring a finned duct, while also addressing challenges associated with dust accumulation. The magnetic field helps to prevent nanoparticle aggregation, enhancing the cooling process. The use of a finned duct combined with a nanofluid as the cooling medium efficiently dissipates excess heat from the silicon layer. Dust accumulation on the glass layer reduces transmissivity, negatively impacting system performance. The magnetic field's interaction with the nanoparticles enhances convective cooling of the upper layer, leading to an overall improvement in performance. Increased pumping power results in higher cooling rates, with improvements of approximately 3.48 % in thermal efficiency (ηth), 75.01 % in thermoelectric generator efficiency (ηTEG), and 39.37 % in photovoltaic efficiency (ηPV). An increase in the Hartmann number (Ha) improves ηth by about 1.87 %, with corresponding enhancements in electrical performance components. A higher concentration of ferrofluid further boosts performance, with the effect being roughly 1.7 times more significant in the absence of MHD compared to when Ha = 97. Dust presence decreases ηth, ηTEG, and ηPV by approximately 9.39 %, 8.55 %, and 25.77 %, respectively. Furthermore, the presence of Ha diminishes the influence of Vin on ηth by around 1.33 %.

Understanding flame behaviors under gradient magnetic fields: The dynamics of non-reacting gas jets

Gradient magnetic fields impact fluid dynamics through Kelvin forces, altering flame behavior. Key complexities such as the interaction of magnetic fields with thermal gradients and chemical reactions within flames remain largely unexplored. By isolating variables such as heat release and thermal convection, this study aims to delve into fundamental mechanisms by which gradient magnetic fields affect the fluid dynamics of flames. This research adopts nitrogen, helium, argon and oxygen as jet gases, focusing exclusively on the fluid dynamics of non-reacting flow. Experimental techniques and Computational Fluid Dynamics (CFD) simulations are employed to explore the effects of varying gas species and magnetic field strengths. Results demonstrate that gas density significantly impacts jet behavior, with paramagnetic oxygen concentrating in areas of stronger magnetic fields, and other gases like helium, nitrogen, and argon showing distinct behaviors based on their molar mass. The study also establishes an optimized energy conservation equation that accurately predict jet height, considering factors such as buoyant and Kelvin forces. By studying the flow behavior of non-reacting gases under magnetic fields, the results are ultimately extended to estimate flame heights and elucidate the mechanisms of air-to-fuel diffusion.

Multi-physics analysis of squeezing fluid flow with rotational, magnetic field, and heat transfer interactions

This research paper presents a comprehensive study on the intricate interplay of rotational, magnetic field and heat transfer effects in squeezing fluid flow, utilizing the foundational framework of Navier–Stokes equations. Fluid flow in confined geometries has significant applications in various industrial processes, including lubrication systems, microfluidics, and heat exchangers. The integration of rotational motion, magnetic fields, and heat transfer phenomena into this context holds immense potential for optimizing performance and efficiency. The study commences with the derivation and analysis of the coupled Navier–Stokes equations, incorporating the Coriolis force due to rotational motion, the Lorentz force arising from magnetic fields, and the energy equation for heat transfer. This comprehensive model accounts for the complex interactions between these physical phenomena, offering a holistic perspective on squeezing fluid flow dynamics. Numerical analysis are conducted to investigate the behavior of fluids under the influence of rotational, magnetic field, and heat transfer effects. The results reveal intricate flow patterns, including vortex formation and heat transfer enhancement. Furthermore, the impact of key parameters such as rotational speed, magnetic field strength, and temperature gradients on flow characteristics is systematically analyzed. The Dufour effect pertains to the transfer of energy resulting from a gradient in mass concentration, occurring as a correlated consequence of irreversible processes. It functions as the inverse of the Soret effect. The temperature changes due to the concentration gradient, amplifying as the Dufour number increases. The most significant temperature rise is observed at the midpoint of the fluid domain. Conversely, the Soret number behaves in a similar but opposite manner. Tables 4–10 has been created to offer a comprehensive analysis of the optimal alignment between Homotopy Analysis Method (HAM) and BVP4c. Specifically, it demonstrates a continuous decrease in skin friction for ξSo, ξRd, and ξR2, while showing an increase for ξSc, ξDo, and ξRem. Meanwhile, the skin friction remains constant for ξPr. The research centers on analyzing heat and mass transfer properties within an incompressible fluid confined between two rotating and stretching disks amidst an unpredictable flow pattern. The study employs a blend of analytical and numerical approaches to solve the governing equations, delving into the intricate fluid dynamics and the intricate processes of heat and mass transfer within this intricate system.

Novel Use of Motor-Evoked Potential Monitoring During Magnetic Resonance Imaging-Guided Soft-Tissue Cryoablation: A Case Report

Motor-evoked potential (MEP) monitoring is an electrophysiologic technique useful for testing peripheral motor nerve integrity during cryoablation cases with risk of nerve injury. Previously, neuromonitoring within the magnetic resonance imaging (MRI) suite for cryoablation has not been performed as magnetic needles are used which could cause magnetic field interactions with neuromonitoring leads. We present the first report of a patient who underwent MEP monitoring during MRI-guided cryoablation of a vascular malformation adjacent to the brachial plexus. We demonstrate that MEPs may be safely and accurately performed by interleaving MRI and MEPs during treatment, reducing the risk of postprocedural complications.

Design of a Permanent Magnet Electromagnetic Acoustic Transducer (EMAT) for In-Situ Inspection of Metals at high Temperatures

In this proposed research, a permanent magnet longitudinal wave Electromagnetic Acoustic Transducer (EMAT) was designed for In-Situ inspection of metals at high temperatures. A permanent magnet EMAT generates Lorentz force inside metals by the interaction of magnetic fields and eddy currents. As temperature rises, various factors can influence the intensity of the Lorentz force, making it difficult to produce and detect ultrasonic waves. Thus, it is essential to optimize the sensor at ambient temperature before attempting to generate a reliable signal at elevated temperatures. The challenge highlighted has been addressed by optimizing the intensity of static field by varying the parameter like spacing between magnets that are being used. In order to minimize the effects of elevated temperatures, the sensor's stability has been enhanced by the implementation of efficient insulating measures. Furthermore, Finite Element (FE) simulations were conducted under on aluminium sample. These simulation results were then compared to experimental data to validate the efficiency of the designed sensor. Keywords: Permanent magnet, EMAT, Lorentz force, ultrasonic waves, high temperature, static magnetic field intensity.

Pulse generators for enhanced magnetomotive ultrasound: Toward a cost-effective imaging for tissue characterization.

Magnetomotive ultrasound (MMUS) stands out as a promising and effective ultrasound-based method for detecting magnetic nanoparticles (MNPs) within tissues. This innovative technique relies on the precise estimation of micrometric displacements induced by the interaction of an external magnetic field with MNPs. Pulsed MMUS has emerged as a strategic alternative to address limitations associated with harmonic excitation, such as heat generation in amplifiers and coils, frequency-dependent tissue mechanical responses, and prolonged magnetic field rise times. Despite the growing interest in MMUS, the devices conventionally employed to excite the coil are not specifically tailored to generate intense magnetic fields while minimizing interference with the transient behavior of induced displacements. To bridge this gap, our work introduces the design and fabrication of two pulse generators: one based on a capacitor-discharge circuit and the other on a resonant-inverter circuit. We evaluated the performance of these pulse generators by considering parameters such as the magnetic field generated, rise and fall times, and their ability to supply sustained current for varied pulse widths across different pulse repetition frequencies. Furthermore, we carried out a practical MMUS implementation using tissue-mimicking phantoms, demonstrating the capability of both devices to achieve magnetic fields of up to 1T and average displacements of 25 µm within the phantom. In addition, we estimated the shear wave velocity, effective shear modulus, and their temperature-dependent variations. Our findings highlight the versatility and efficacy of the proposed pulse generators and emphasize their potential as low-cost platforms for theranostic applications, enabling the assessment of targeted entities within biological tissues.

Magnetic dissipation on radiative free convection of a conducting hybrid nanofluid within a rotating cone and circular disc

A significant attention is gained on the thermophysical properties corresponding to hybrid nanofluid flow within a rotating cone and circular disc in this present investigation due to its several applications. The enhanced thermal conductivity of the nanofluid is particularly useful in cooling systems, reducing energy consumption in systems, preventing overheating, and improving the overall performance of electronic gadgets, etc. In the present investigation, the free convective flow of conducting fluid for the interaction of magnetic field and thermal radiation encases their greater impact on the flow phenomena. Further, the assumption of dissipative heat i.e. mutual effects of viscous and Joule, energies the flow properties. The complex nonlinear form of the constitutive equations presented in the dimensional form is renovated into the nonlinear ordinary system with a non-dimensional form by introducing suitable similarity rules. The computation of the profiles is obtained numerically with the help of the built-in function bvp4c in MATLAB and depicted graphically. Finally, it is observed that the volume fraction of both the nanoparticles favors enhancing the heat transport phenomena due to the augmented thermal conductivity whereas a dual characteristic is revealed at both the surfaces of the circular disc and the cone.

Effect of permanent magnetic field on photoluminescence of barium and calcium nanofluorides

This work establishes for the first time that imposing of permanent magnetic field ledt o shift of peaks in ranges of photoluminescence of nanopowders CaF2 and BaF2. Ranges of shift of peaks to the red area of a spectrum depended on the size of magnetic field. A transformation of peaks occurs as a result of interaction of own magnetic field of nanofluorides with external magnetic field caused by structural defects of nanopowders. Deconvolution of spectra allowed to identify the split of the first peak of both nanofluorides to a quadruplet, and the second to a doublet at the size of magnetic field of 0.1 T. At increase in magnetic field the quadruplet of the first peak disappears, and the doublet of the second significantly differs for ferromagnetic CaF2 and para-ferromagnetic BaF2. Besides, spectra of both nanofluorides contain peaks at 616 nm that aren’t observed in the field of 0.1 T but appear in the field of 0.15 T, and are possibly caused by the center of coloring.

AC transport loss analysis of HTS stack busbars for all-electric aircraft with harmonics and DC offset considerations

This paper presents a study of the current carrying capacity and AC loss of high-temperature superconducting (HTS) stacks to be used in busbar applications for all-electric aircraft. A 2D model was developed using COMSOL Multiphysics with a T-A formulation for detailed analysis. The study began by applying a stable 20 kA DC offset current to the HTS stacks to simulate practical operating conditions. Firstly, the behaviour of the critical current was studied under self-field conditions for stacks with different numbers of HTS tapes and spacing. Secondly, AC ripple currents were introduced with DC offsets, and the effects of 3rd and 5th harmonic distortions (HD) were studied. The results show that configurations with 40 tapes and gaps of more than 2 mm are considered suitable for safe current transport under DC conditions. On the other hand, increasing the tape spacing leads to an increase in the safe transport current ripple due to the reduced magnetic field interaction within the stack. In addition, the transport loss decreases as the air gap increases due to the reduction in the self-field, whereas it increases as the number of strips increases. The influence of the 3rd HD on the transport loss is minimal at a ripple current of 1% and slightly noticeable at 2%. However, it becomes more obvious as the ripple current approaches the critical value. Remarkably, even cases with equivalent total HD show significantly higher transport losses when characterised by higher 5th HD than their counterparts with 3rd HD. This comprehensive analysis provides valuable information on the performance characteristics of HTS stacks in all-electric aircraft busbar applications and offers important insights for the development and optimisation of these systems in practical aerospace applications.

Unsteady Dean flow between concentric circular cylinders in the presence of a uniform axial magnetic field

An analysis is carried out on the unsteady Dean flow of an incompressible electrically conducting viscous fluid between two concentric, stationary permeable circular cylinders in the presence of magnetic field of low intensity. The flow phenomenon is important in view of its biological as well as industrial applications, particularly in polymer industries for designing flows in cylindrical shaped pipes/tubes. The novelty of the study is to analyze the effect of electromagnetic body force which comes into play due to interaction of magnetic field with conducting fluid in flow. The cross flow due to suction/injection, azimuthal pressure gradient, and the Lorentz force (electromagnetic body force) are considered in the momentum transport equation. The mathematical model and the corresponding governing equations are solved in two methods; one is analytical using special function and another one is semi analytical approach, i.e. Laplace transform in conjuction with Riemann–Sum approximation for inversion. The study reveals the effects of magnetic parameter, suction/injection parameter and radii ratio of two concentric cylinders forming annular region. The striking outcomes which fulfills the design requirements are as follows. The applied radial magnetic field resulting electromagnetic body force on the flow, accelerates the circumferential velocity which energizes the industrial setup (flow model) to enhance faster productivity. Moreover, the curves of skin friction at R = λ posses critical points serving as benchmark for engendering flow instability.

Signs of dynamic nonlinearity of the coal dielectrics depolarization upon excitation in electric and magnetic field

The authors conducted a series of experiments on samples treated immediately before measurements with a constant magnetic field of a neodymium magnet and/or an alternating electric field. The experiment has shown complex dynamics of electric potential with alternating polarity relative to the base exponential depolarization curve. The variety of responses to different types of excitation, and the irregular and unpredictable nature of fluctuations suggest that these are varieties of the same phenomenon – the nonlinear dynamics of ferroelectric domains. The applied methods of statistical processing of the cumulative data array suggest that the invariance of the relaxation dynamics of the accumulated electric potential after excitation can be characterized by three related nonlinear differential equations of the first order. The impact of an alternating electric field may consist in bringing the dipoles of ferroelectric domains in the molecular coal structure into a state of unstable equilibrium with their slow return to their original position. The impact of a constant magnetic field is determined by the interaction of the external magnetic field with the magnetization induced due to time-varying electric polarization. In any case, the observed fluctuations are due to changes in the domain structure topology of the condenser with coal matter.

Magnetic-induced chiral dynamics in an extended two-leg bosonic ladder

The realization and detection of chiral physics with ultracold atomic gases provide a unique path for the exploration of topological phases. Here, we show that the interplay of magnetic field and interacting particles in an extended two-leg ladder leads to rich chiral Bloch dynamics. Considering both the on-site contact interaction and nearest-neighbor interactions, the ground state and Bloch dynamics of the system are studied analytically and numerically. When the system is in the ground state, the threshold and phase diagram for the transition between zero-momentum state and plane-wave state are analytically obtained, showing the nearest-neighbor interactions along the legs and rungs have opposite impact on the ground state transition, providing new opportunity to manipulate the ground state transition. When the ladder is perturbated under an external linear force, chiral dephasing of Bloch oscillations (BOs), i.e. symmetry breaking damped BOs (the damping rate of BOs on one leg is larger than the other), are observed. This chirality is absent for vanishing the magnetic field and atomic interaction. Particularly, the chirality of damped BOs is inversed when the magnetic field (chiral current) is inversed. In addition, the damping of BOs induced by different types of atomic interactions is different, and the strength and damping rate of BOs initialized in different ground states are distinct, offering dynamic ways to detect the different ground states. Furthermore, the persistent chiral Bloch oscillations observed in single particle case is predicted analytically, which is a crucial requirement for observation and application of chiral BOs in nonlinear regime. Our results provide an interesting path towards the exploration of topological atomic superfluids.

Examination of Magnetic Field Signatures and Local Plasma Distribution Variations in Jupiter's Magnetosphere

AbstractSpinning disk of plasma results in deformation of Jupiter's magnetic field from a dipole to a magnetodisc configuration with significant radial and azimuthal components. Polar orbit of the Juno spacecraft enables a comprehensive in situ observation of Jupiter's plasmadisc at different latitudes. Observations from magnetometer and plasma distribution instruments on Juno mission were used to examine interaction of magnetic field and heavy ions in Jupiter's nightside magnetosphere. Power spectrum analysis was used to evaluate magnetic fluctuations inside and outside of the plasmadisc. Extensive radial maps of magnetic activity in Jupiter's nightside magnetosphere are presented. Comprehensive examination of magnetic fluctuations enable to identify local plasma density variations that correlate with plasma distribution count rate fluctuations. Observations of magnetic signatures together with examination of plasma distribution are used to detect features that point to plasma transport inside and outside of Jupiter's plasmadisc. This work shows that plasma in Jupiter's magnetosphere is contained near centrifugal equator and is not a subject to curvature drift that could generate ring currents. Signatures described as current sheet crossings were investigated. On close inspection these signatures show attributes that belong to stand alone formations rather than a single current sheet structure. This work shows that current flow is not an adequate mechanism to explain deformation of Jupiter's magnetic field.

Magnetic field impact on ferronanofluid laminar flow

A comprehensive understanding of the magnetic field interaction with the flow of ferronanofluids is essential to determine the heat transfer effect and the potential for use in industrial applications. The purpose of this work is to determine the effects of magnetic field orientation and intensity, as well as inertia forces, on heat transfer in the laminar flow of a ferronanofluid. The experiment involved the use of five permanent magnets positioned both below and above the flowing magnetite-based ferronanofluid. The analysis of the effect on heat transfer is carried out using the similarity numbers, Reynolds number (ratio of inertia and viscous forces), magnetic number (ratio of magnetic and inertia forces) and product of the two (ratio of magnetic and viscous forces).The findings indicate that the orientation of the magnetic field relative to temperature gradient-induced secondary motions plays a crucial role in either enhancing or inhibiting heat transfer. The magnet positioned below the flow leads to improved heat transfer, while placement above hinders it. To determine the magnetic field effect on heat transfer, the ratio of magnetic to viscous force introduced as MnRe is used. Taking the 5 % Nusselt number change as the threshold, the critical value for the orientation of magnet above the tube is MnRe = 24,000, while for the configuration with the magnet below, MnRe = 32,000 for Re = 109 and MnRe = 88,000 for Re = 150 and 163. The magnetic field effect is local and diminishes as the fluid flows, ultimately causing the heat transfer parameters to revert to their reference state. However, an increase in the ratio of inertia and viscosity forces enables the magnetic field interaction effect to propagate over a longer distance.

Effect of the magnetic field on the conductance and spin polarization in phosphorene superlattice

The spin-dependent conductance and spin polarization are investigated theoretically in a phosphorene superlattice in the presence of external magnetic field and Rashba interaction. It is demonstrate that, the spin-dependent conductance with and without spin-flip as well as spin polarization can be effectively controlled by changing the magnetic field strength and the number of the superlattice barriers. For small magnetic field strength, the conductance for with and without spin-flip shows an oscillating behavior as increasing the strength of the Rashba interaction, and by increasing the number of barriers, the oscillating behavior becomes prominent. Further, when the magnetic field is greater than a limit value, the spin conductance will be zero. The size of the spin-dependent transmission window in the phosphorene superlattice under external magnetic field decreases drastically. The magnitude, sign and behavior of the spin polarization can be tuned by the amount of the external magnetic field.