Sinusoidal Magnetic Field Research Articles

A method for data conversion of exposure level testers using sinusoidal alternating magnetic fields

Flux density measurements provide valuable information on the state of electrical appliances, which can be utilised for improving the safety and the performance of the associated system. Exposure level testers with a B-field probe are widely used for flux density measurements but they can only perform a time-domain measurement and display it as output voltage related to flux density. In other words, they cannot output flux density directly, which brings many inconveniences. These drawbacks can be improved using data conversion coefficients. However, the test frequencies of most exposure level testers are greater than 1 Hz. They are unable to calculate the data conversion coefficients using a constant magnetic field. This paper proposes a method for data conversion of exposure level testers using alternating magnetic fields to measure flux density directly: the flux density conversion model was established; the mathematical relationship between the mean value of the voltage signal output by the exposure level testers and its stable display value was deduced; and an experimental test of the conversion coefficients was carried out. The results show that the error between the value measured using the new technique and the display value of the exposure level tester at different frequencies is small. This method can trace the flux density in both the time and frequency domains through software processing algorithms without changing the exposure level tester itself. By applying sinusoidal magnetic fields and using the conversion factor, then existing testers can be used to measure flux density directly.

Effect of the dipolar interaction on the dynamic hysteresis of properties of 2D-nanodisks: In-plane driving field case

The effect of the dipolar interaction strength on the dynamical hysteresis behavior of the nanodisk is investigated within the Heisenberg model and Monte Carlo simulation. The system is under the effect of the dynamical periodic sinusoidal magnetic field. It has been shown that dipolar interaction strength can induce dynamical phase transition and the transition from the fully dynamically ordered ground state to the weak dynamically ordered ground state. Besides, it has been shown that rising dipolar interaction raises the hysteresis loop area for higher temperatures and a linear relationship between the peak positions of the hysteresis loop area and the temperature locations of the peaks obtained.

Non-linear radiative second-grade nano fluid with sinusoidal magnetic force and arrhenius activation energy: A computational exploration

The goal of this work is to further improve our knowledge of the nonlinear radiative second-grade nano fluid flow boundary layer phenomena which is associated with an Arrhenius activation energy, a sinusoidal magnetic field, and a stretched peripheral with a heat source. The unsteady governing equations are transformed into a proper dimensionless arrangement, and then the explicit finite difference (EFD) method is applied to numerically calculate the equations. However, precise stability and convergence criteria have been developed to make the solution convergent. Along with the typical profile of other flow fields, the oscillatory forms of the velocity are shown. Tabular research has even demonstrated a relationship between the Nusselt number and other parameters, and graphical depiction has been used for regression and data prediction. The novel conclusions drawn from this research indicate that, in comparison to linear patterns, nonlinear radiative heat flux significantly raises (30.35 %) flow profiles with second-grade characteristics. Moreover, the heat transfer rates of second-grade Nano fluids are seen to be significantly influenced (35.14 %) by the sinusoidal magnetic component. When considering nonlinear thermal radiation, activation energy principles cause a major change (34.19 % more) in mass transmission, as high-temperature processes become an essential part of chemical reactions.

Dichotomous dynamics of magnetic monopole fluids

A recent advance in the study of emergent magnetic monopoles was the discovery that monopole motion is restricted to dynamical fractal trajectories [J. N. Hallén et al., Science 378, 1218 (2022)], thus explaining the characteristics of magnetic monopole noise spectra [R. Dusad et al., Nature 571, 234 (2019); A. M. Samarakoon et al., Proc. Natl. Acad. Sci. U.S.A. 119, e2117453119 (2022)]. Here, we apply this novel theory to explore the dynamics of field-driven monopole currents, finding them composed of two quite distinct transport processes: initially swift fractal rearrangements of local monopole configurations followed by conventional monopole diffusion. This theory also predicts a characteristic frequency dependence of the dissipative loss angle for AC field-driven currents. To explore these novel perspectives on monopole transport, we introduce simultaneous monopole current control and measurement techniques using SQUID-based monopole current sensors. For the canonical material Dy2Ti2O7, we measure [Formula: see text], the time dependence of magnetic flux threading the sample when a net monopole current [Formula: see text] is generated by applying an external magnetic field [Formula: see text] These experiments find a sharp dichotomy of monopole currents, separated by their distinct relaxation time constants before and after t ~[Formula: see text] from monopole current initiation. Application of sinusoidal magnetic fields [Formula: see text] generates oscillating monopole currents whose loss angle [Formula: see text] exhibits a characteristic transition at frequency [Formula: see text] over the same temperature range. Finally, the magnetic noise power is also dichotomic, diminishing sharply after t ~[Formula: see text]. This complex phenomenology represents an unprecedented form of dynamical heterogeneity generated by the interplay of fractionalization and local spin configurational symmetry.

Thresholds and mechanisms of human magnetophosphene perception induced by low frequency sinusoidal magnetic fields

BackgroundVirtually everyone is exposed to power-frequency MF (50/60 Hz), inducing in our body electric fields and currents, potentially modulating brain function. MF-induced electric fields within the central nervous system can generate flickering visual perceptions (magnetophosphenes), which form the basis of international MF exposure guidelines and recommendations protecting workers and the general public. However, magnetophosphene perception thresholds were estimated 40 years ago in a small, unreplicated study with significant uncertainties and leaving open the question of the involved interaction site. MethodsWe used a stimulation modality termed transcranial alternating magnetic stimulation (tAMS), delivering in situ sinusoidal electric fields comparable to transcranial alternating current stimulation (tACS). Magnetophosphene perception was quantified in 81 volunteers exposed to MF (eye or occipital exposure) between 0 and 50 mT at frequencies of 20, 50, 60 and 100 Hz. ResultsReliable magnetophosphene perception was induced with tAMS without any scalp sensation, a major advantage as compared to tACS. Frequency-dependent thresholds were quantified using binary logistic regressions hence allowing to establish condition dependent probabilities of perception. Results support an interaction between induced current density and retinal rod cells. ConclusionBeyond fundamental and immediate implications for international safety guidelines, and for identifying the interaction site underlying phosphene perception (ubiquitous in tACS experiments), our results support exploring the potential of tAMS for the differential diagnosis of retinal disorders and neuromodulation therapy.

Unveiling the influence of fixed layer polarization on skyrmion nucleation and dynamics in circular geometry

Chiral magnetic skyrmion spin textures promise to be the next generation of energy-efficient computing. An effective way of skyrmion creation is essential to use as an information carrier. We report the creation of a skyrmion in a circular spin valve nanostructure using spin-polarized currents. This research investigates skyrmion nucleation under perpendicular and vortex fixed layer polarizations. The impact of Dzyaloshinskii-Moriya interaction (DMI), magnetic anisotropy, and saturation magnetization on the nucleation process has been studied for the perpendicular case. Depending on fixed layer polarization, we observed a trade-off between current density and pulse width for skyrmion nucleation. Vortex polarization enables faster nucleation at higher currents, while perpendicular polarization facilitates lower current thresholds at the expense of longer pulses. Further skyrmion dynamics have been explored under the sinusoidal magnetic fields.

Entropy analysis in a mixed convective Carreau nanofluid flow around a wedge: impact of activation energy and sinusoidal magnetic field

A wide range of real-world applications have proven the importance of non-Newtonian fluids near a wedge, including the oil and gas industry, the aerospace sector. This study elucidates the dynamics of a Carreau nanofluid around a wedge by combining entropy analysis with periodic magnetohydrodynamics (MHD) and activation energy. The dimensional partial differential equations (PDEs) that describe the fluid flow system undergo non-similar transformations, forming nondimensional PDEs. The numerical solution to these PDEs is obtained by applying quasilinearization followed by the implicit finite difference approach. In the case of n = 0.5 (power-law index), when We (Weissenberg number) improves from 0 to 4, surface friction ( R e 1 / 2 C f ) upsurges by approximately 23% and declines by around 41% in the case of n = 1.5. The mass transport intensity of liquid oxygen is about 18% higher than liquid nitrogen’s. Increasing the wedge angle results in a significant increase in fluid velocity.

Micromagnetic investigation of dynamic hysteresis and dynamic phase transition properties in Co, Fe and Ni nanodisks

We have investigated the dynamical hysteresis behaviors of Co,Fe, and Ni nanodisks under the effect of the time-dependent magnetic field by solving the Landau-Lifshitz-Gilbert equation with the OOMMF software. A nanodisk with a diameter of 360nm constructed in the xy plane is exposed to a sinusoidal x-directed magnetic field with varying frequency and amplitude values. All nanodisks exhibit intricate frequency-dependent variations in the hysteresis loop area, remanent magnetization, and coercive field. Our simulation results emphasize that while the dynamical order occurs exclusively in the x direction for Fe nanodisks, dynamical order is observed in the y and z directions for Ni nanodisks within a specific frequency range.

Magnetic particle spectroscopy and magnetic particle imaging of zinc and cobalt ferrite nanoparticles: Distinct relaxation mechanisms

Magnetic particle imaging (MPI) is an emerging imaging method based on the nonlinear response of superparamagnetic tracers to a sinusoidal AC magnetic field. Higher harmonics obtained by the Fourier transform of acquired signals form a so-called magnetic particle spectrum, whereby straightforward evaluation of different nanoparticles as potential MPI tracers can be carried out. The shape of the spectra is largely dictated by the combined Néel and Brownian relaxation of superspins, whose relative contributions vary significantly depending on the tracer properties. The present study is focused on the comparison of several Zn ferrite and Co ferrite samples, selected for their different magnetic behaviors, together with the commercial tracer Resovist® (SH U 555 A). A new custom-made magnetic particle spectrometer and a commercial MPI system (Bruker) with comparable AC field amplitudes (∼14 mT) and frequencies (∼25 kHz) are used. Magnetic nanoparticles of Zn and Co ferrites have been synthesized by the thermal decomposition method and by the solvothermal/hydrothermal route, achieving four different samples of magnetic cores with the mean crystallite size in the range of 8–16 nm. From all of them, well-comparable silica-coated particles with a shell thickness of 5–6 nm have been prepared. To analyse the effect of the coating layer and hydrodynamic size, three additional samples have been supplemented: solvothermal Zn ferrite nanoparticles stabilized with a citrate monolayer, the same particles coated with 17 nm thick silica shell, and silica-coated Zn ferrite particles from the thermal decomposition with a higher degree of agglomeration. Fundamental characterizations of the nanomaterials by XRD, XRF, TEM, and DLS are followed by detailed investigations of their magnetic properties and structural peculiarities by SQUID magnetometry and 57Fe Mössbauer spectroscopy. Magnetic particle spectroscopy and subsequent MPI study demonstrate: (i) superior properties of Zn ferrite nanoparticles compared to their Co ferrite counterparts, (ii) only negligible to weak effect of the type/thickness of the coating on signal of Zn ferrite nanoparticles, (iii) comparable performance of the solvothermal Zn ferrite particles with a thin silica shell and of the Resovist® tracer, and importantly, (iv) that suitable choice of the magnetic phase enables to separate the contributions of the Néel and Brownian relaxation on the timescale of MPI.

No mutation effect of 50 Hz sinusoidal magnetic field on beta catenin gene phosphorylation site in N-methyl-N-nitrosourea (MNU) induced colon tumor model

No mutation effect of 50 Hz sinusoidal magnetic field on beta catenin gene phosphorylation site in N-methyl-N-nitrosourea (MNU) induced colon tumor model

A Novel Tactile Sensing System Utilizing Magnetorheological Structures for Dynamic Contraction and Relaxation Motions.

It is well known that the rheological properties of magnetorheological (MR) material change under a magnetic field. So far, most works on MR materials have been oriented toward actuating characteristics instead of sensing functions. In this work, to realize dynamic tactile motion, a spherical MR structure was designed as a sensor, incorporating a magnetic circuit core to provide maximum dynamic motion. After manufacturing a prototype (sample), a sinusoidal magnetic field of varying exciting frequency and magnitude was applied to the sample, and the dynamic contraction and relaxation motion depending on the exciting magnetic field was observed. Among the test results, when 10% deformation occurred, the instantaneous force generated was from 2.8 N to 8.8 N, and the force when relaxed was from 1.2 N to 3.5 N. It is also shown that the repulsive force within this range can be implemented using an acceptable input current. The special tactile sensing structure proposed in this work can be used as a sensor to measure the field-dependent viscoelastic properties of human tissues such as stomach, liver, and overall body. In addition, it could be usefully applied to robot surgery, because it can mimic the dynamic motions of various human organs under various surgical conditions.

Low-Concentration Magnetic Particle Spectroscopy Using Gradiometric Receive Coil-Coupled Magnetoresistive Sensor

In order to realize clinical magnetic particle imaging (MPI), scanner sensitivity must be designed to recognize magnetic nanotracers within safe dosage range. As zero-dimensional MPI scanner, magnetic particle spectroscopy (MPS) is often used to initially characterize complex dynamic of the tracers by applying a sinusoidal magnetic field with high amplitude. However, the resulting magnetization signal can be very small to dominate electromagnetism of cellular matrices with tracer concentration below 2 μg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fe</sub> mL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Here, we demonstrated an enhanced MPS sensitivity by coupling typical gradiometric receive coil with a magnetoresistive (MR) sensor under 25 mT/μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at 10 kHz. This magnetometric system could distinguish particle signal of Resovist® sample from its 0.1mL liquid medium while diluting iron concentration up to 70 ng <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fe</sub> . For this case, we confirmed that the field-induced background signal from water-based medium became significant. Depending on ion concentration, such polar solvent exhibited both diamagnetism and Eddy current effect. Even though its harmonic components might disappear technically, magnetization signal of low-concentration sample had phase and magnitude differences relative to those of the medium at fundamental frequency. Owing to its high sensitivity, MPS system using MR sensor can be potentially implemented for liquid-phase biosensing, in addition to MPI technology.

Investigation of harmonic and inharmonic domain wall oscillation by sinusoidal magnetic field in the notched Permalloy nanowire using micromagnetic approach

In this work, the harmonic and inharmonic domain wall (DW) oscillations by sinusoidal magnetic field in double triangular notched Permalloy nanowires were investigated by micromagnetic simulation. The simulation results show the DW resonant frequencies were linearly related to the induced field frequency. It is shown that in the wire thickness of 2.5 ​nm, there is a minimum value of sinusoidal field frequency so that the DW can be harmonically oscillating as the induced magnetic field. Below the certain value, the DW will be moving out of the notch as depinning process occurs. In the higher frequency, the DW resonant frequency fluctuates and the phase-lag is larger, so that the DW oscillates inharmonically with the injected sinusoidal field and the resonant frequency decreases significantly. These phenomena could be understood by the slight change of the DW approximated mass as its position shifted around notch area. Therefore, the understanding of DW structures and dynamics under the effect of oscillating magnetic field could be a consideration on the selection of optimized nanowire geometries in the development of the domain wall-based memory storage system.

Pulsed magnetic field increases the effect of ultraviolet C radiation and thermal shock in aged yeasts

The study of the effects of the magnetic field (MF) on living matter continues to be a dilemma. Until now, the interaction mechanisms of MF with living matter that explain the observed phenomena are unknown. Despite the existing literature and the multiple effects described to date, there are few published articles that study the combined effect of MF with other physical agents during the cellular aging process. In this sense, the aim of this work is to study whether low frequency and intensity pulsed and sinusoidal MF exposure produce alterations in the cell killing effect of ultraviolet C (UVC) radiation and thermal shock during the chronological aging of S. cerevisiae. Yeast cells were exposed to 2.45 mT (50 Hz) sinusoidal MF and 1.5 mT (25 Hz) pulsed MF, during 40 days of aging, in combination with UVC radiation (50 J/m2) and/or thermal shock (52°C). Cell survival was evaluated by clonogenic assay. The exposure of yeast to pulsed MF produces an acceleration of aging, which is not observed in cells exposed to sinusoidal MF. The pulsed MF modifies the cellular response to damaging agents only in aged S. cerevisiae cells. In this sense, the pulsed MF applied increases the damage induced by UVC radiation and by thermal shock. In contrast, the sinusoidal MF used has no effect.

Dynamics of ferrimagnetic domain walls driven by sinusoidal microwave magnetic field

Ferrimagnetic domain walls have received more and more attention because of their interesting physics and potential applications in future spintronic devices, particularly attributing their non-zero net magnetization and ultrafast dynamics. Exploring effective methods of driving domain walls with low energy consumption and high efficiency can provide important information for experimental design and device development. In this work, we study theoretically and numerically the dynamics of ferrimagnetic domain wall driven by the sinusoidal microwave magnetic field using the collective coordinate theory and Landau-Lifshitz-Gilbert simulations of atomistic spin model. It is revealed that the microwave field drives the propagation of the domain wall when the frequency falls into an appropriate range, which allows one to modulate the domain wall dynamics through tuning field frequency. Specifically, below the critical frequency, the domain wall velocity is proportional to the field frequency and the net angular momentum, while above the critical frequency, the domain wall velocity decreases rapidly to zero . The physical mechanisms of the results are discussed in detail, and the influences of the biaxial anisotropy and other parameters on the velocity of domain wall are studied. It is suggested that the wall dynamics can be effectively regulated by adjusting the basic magnetic structure and magnetic anisotropy, in addition to the external microwave field frequency. This work uncovers the interesting dynamics of ferrimagnetic domain wall driven by sinusoidal microwave magnetic field, which is helpful for designing domain wall-based spintronic device.

Dynamic Magnetic Features of a Mixed‐Spin‐2 and Spin‐5/2 Ising Ferrimagnetic System under a Time‐Dependent Oscillating Magnetic Field: Path Probability Method Approach

A study, within the path probability method, of the dynamic magnetic features of the mixed spin (2, 5/2) Ising ferrimagnetic system on a hexagonal lattice under the presence of a sinusoidal external magnetic field is presented. The Hamiltonian of the system contains intersublattice, intrasublattice, and crystal‐field interactions. The intersublattice interaction is taken as antiferromagnetic. The time variations of average dynamic magnetizations and the thermal behavior of the dynamic magnetizations are investigated to obtain the phases in the system and to characterize the nature of the dynamic phase transitions and find the dynamic phase transition temperature points. The dynamic phase diagrams in six different phase planes are presented, in which they contain the paramagnetic (p) phase, three different ferrimagnetic (i 1, i 2, i 3) fundamentals, and the p + i 1, i 1 + i 2, and i 2 + i 3 mixed phases as well as the dynamic tricritical point and the dynamic double critical end point, depending on the interaction parameters. The dynamic compensation behavior is also examined and only N‐type behaviors are observed. Some of the obtained dynamic phase diagrams are in qualitatively good agreement within some works on the dynamics of mixed‐spin Ising system.

Sensitivity and reproducibility of transverse magneto-optical Kerr effect (T-MOKE) ellipsometry

We report a comprehensive experimental study to analyze the limiting factors and physical mechanisms that determine the achievable performance of transverse magneto-optical Kerr effect (T-MOKE) ellipsometry. Specifically, we explore different approaches to achieve high sensitivity and reduced acquisition times. The best sensitivity is observed for an incident light polarization with balanced s-p components. We also verify experimentally that the method’s theoretical description is accurately describing data for any s-p combination of the incoming light. Furthermore, two alternative measurement strategies are explored by using different measurement sequences for the polarization sensitive optics, which both achieve a very comparable, high quality of results. Signal-to-noise ratios and systematic deviations are measured and analyzed based on a large number of nominally identical measurement repeats, both for entire signal sequences as well as for individual Fourier components of the magneto-optical signal generated by a sinusoidal magnetic field sequence. Hereby, we observe that while higher order Fourier components have a significantly reduced signal amplitude and correspondingly exhibit reduced signal-to-noise and repeatability performance, signal-to-noise ratios always exceed values of 100 even for the lowest signal Fourier component and the lowest signal sample that we investigated, illustrating the extremely precise nature of T-MOKE ellipsometry.

Regulation of LTP at rat hippocampal Schaffer-CA1 in vitro by musical rhythmic magnetic fields generated by red-pink (soothing) music tracks

Purpose Music therapy, like red-pink (soothing) music, is an important treatment for neurological disorders associated with learning and memory. Magnetic fields have been proved to have a similar regulating effect. However, the effect of magnetic fields with musical rhythm generated by the combination of the two has not been confirmed. This study aimed to investigate the regulation of magnetic stimulation with music rhythm on LTP (long-term potentiation) of Schaffer-CA1. Materials and methods This article selected three sorts of music tracks in different frequencies (music track (1) Turkish March, music track (2) Moonlight Sonata, music track (3) Funeral March) and four sorts of pure sinusoidal tracks of four different harmonic frequency (music track (4) the frequency is 3500 Hz; music track (5) the frequency is 2500 Hz; music track (6) the frequency is 1500 Hz; music track (7) the frequency is 500 Hz). These music tracks are converted into analog signals by the external sound card and power amplifier and fed into a homemade coil that meets the demand for this frequency bandwidth. The coil can generate seven sorts of time-varying magnetic fields with musical rhythm with a mean intensity of about 2 mT. We used multi-electrode array (MEA) to record the LTP signals of Schaffer-CA1 synaptic induced by seven sorts of musical rhythmic magnetic fields and analyze the regulation of them. Results The musical rhythmic magnetic fields generated by track 1 and track 2 have a remarkable enhancing effect on the amplitude of fEPSPs (field excitatory postsynaptic potentials) (p < .05), and these effects intensify with the increase of frequency. Nevertheless, there is no significant enhancing effect on LTP of the rhythmic magnetic field generated by track 3 (p > .05). The sinusoidal magnetic fields generated by track 4 and track 5 have an enhancing effect on the amplitude of fEPSPs (p < .05), and the enhancement is better than track 1 and track 2. The sinusoidal magnetic fields generated by track 6 and track 7 have an inhibiting effect (p < .05). Conclusion We found that the enhancing effect of musical rhythmic magnetic fields generated by track 1 was the most significant. The frequency of 1500 Hz could be a turning-point frequency in the regulation of magnetic field on LTP.

Field exposure to 50 Hz significantly affects wild-type and unfolded p53 expression in NB69 neuroblastoma cells.

Previous studies have shown that intermittent exposure to a 50 Hz, 100 µT sinusoidal magnetic field (MF) promotes proliferation of human neuroblastoma cells, NB69. This effect is mediated by activation of the epidermal growth factor receptor through a free radical-dependent activation of the p38 pathway. The present study investigated the possibility that the oxidative stress-sensitive protein p53 is a potential target of the MF, and that field exposure can affect the protein expression. To that end, NB69 cells were exposed to short intervals of 30 to 120 min to the aforementioned MF parameters. Two specific anti-p53 antibodies that allow discrimination between the wild and unfolded forms of p53 were used to study the expression and cellular distribution of both isoforms of the protein. The expression of the antiapoptotic protein Bcl-2, whose regulation is mediated by p53, was also analyzed. The obtained results revealed that MF exposure induced increases in p53 gene expression and in protein expression of the wild-type form of p53. Field exposure also caused overexpression of the unfolded form of p53, together with changes in the nuclear/cytoplasmic distribution of both forms of the protein. The expression of protein Bcl-2 was also significantly increased in response to the MF. As a whole, these results indicated that the MF is capable of interacting with the function, distribution and conformation of protein p53. Such interactions could be involved in previously reported MF effects on NB69 proliferation promotion.

Dynamic hysteresis features of a mixed spin (1/2, 3/2) Ising system within the path probability method

ABSTRACT The dynamic hysteresis features (DHFs) of a mixed spin (1/2, 3/2) model on a square lattice was studied within the path probability method (PPM) in the presence of a time-varying (sinusoidal) magnetic field. The PPM contains three rate constants in which one of them (k 2) may be considered as corresponding to the wheel speed in the melt-spinning method (MSM). Influences of the temperature (T), angular frequency (ω), and the rate constant (k2 ) on the DHFs for the attractive bilinear interaction were examined. We also investigated the magnetic coercive fields and remanent magnetizations as functions T, ω, and k 2. Some of our obtained results are in qualitatively good agreement with some theoretical studies, experimental reported works on some magnetic materials, and the hysteresis loops obtained by using the MSM.