External Static Magnetic Field Research Articles

Routing emission with a multi-channel nonreciprocal waveguide

In this work, we present a multi-channel nonreciprocal waveguide, which is composed of a gyrotropic-bounded dielectric on the bottom and a plasmonic material on the top. The Lorentz reciprocity in the time-invariant system is broken when applying an external static magnetic field on the gyrotropic material. The nonreciprocal emission from the dipole source located in the center of the waveguide is observed in extended waveband channels. The proposed heterostructure serves as a photonic dichroism once the dielectric is replaced by a nonlinear material. The associated second harmonic generated in the nonlinear process can be separated from the fundamental signal under proper magnetic field intensity. Our findings may provide significant guidance for designing nonreciprocal photonic devices with superiorities of a tunable waveband, multiple channels, and small footprint.

Electromagnetic energy rotation by azimuthal surface waves along plasma-metal interface around a cylindrical metallic rod placed into infinite magnetized plasma

Electromagnetic energy rotation around a cylindrical metallic rod placed into an infinite plasma, parallel to an external static uniform magnetic field, is studied. Angular phase velocity and angular velocity of energy transport are introduced and analyzed as functions of the plasma waveguide parameters: rod radius, plasma particle density, azimuthal wave number, and external static axial magnetic field. These angular velocities are compared with the case of wave propagation in cylindrical metallic waveguides entirely filled by magnetoactive plasma.

Recent advances in the use of magnetic nanoparticles to promote neuroregeneration.

Recent advances in the use of magnetic nanoparticles to promote neuroregeneration.

Self-diffusion of ethylammonium nitrate ionic liquid confined between modified polar glasses

Ethylammonium nitrate (EAN) ionic liquid confined between flat polar glass plates demonstrates variable diffusivity that is sensitive to an external static magnetic field. Outside the magnetic field, diffusivity between the plates is higher than that in the bulk. However, after placing the system in a strong static magnetic field, the diffusivity gradually decreased. These processes occur during transformations between phases formed in EAN subjected to micrometer-size restrictions outside and within the magnetic field (Filippov et al., J. Mol. Liq. [2018] 268, 49). In this study, we used samples of two types: (i) with roughened surface formed by treatment of the glass plates with aqueous solutions of hydrofluoric acid and (ii) with vacuum deposited TiO2 layers with a thickness of ca. 1 μm at glass-plate edges. Neither the surface modification of the glass plates, nor the TiO2 layers controlled thickness of EAN confined between glass-plates significantly changed the above-described effects, which have been observed in studies using untreated glass plates. Therefore, the range of systems with detected phase transformations in EAN and accompanying effects, such as accelerated diffusivity and change in diffusivity under the influence of a static magnetic field, was expanded to the systems with roughened surfaces and the systems with TiO2 layers controlled inter-plates distances. Results of experiments with roughened surfaces additionally suggested that the phase transformation of confined EAN in the external magnetic field is isotropic in nature rather than a phase transition from “layered to bulk” structures.

Initial stage of interaction between gyrating relativistic electron beam and long-wavelength electromagnetic surface waves in cylindrical metallic waveguides partially filled with plasma

Azimuthal surface waves are eigen electromagnetic waves of cylindrical metallic waveguides with plasma filling. Azimuthal surface waves of extraordinary polarization are known to be effectively excited by a beam of electrons gyrating in an axial external static magnetic field along large Larmor radii around the plasma column. Beam excitation of azimuthal surface waves was well studied theoretically in both linear and nonlinear approaches. An important limitation of the earlier studies was the approximation of zero axial wavenumber. In the present paper, perturbation theory is applied to account for finite magnitude of the axial wavenumber of electromagnetic surface waves in studying their excitation by an electron beam. The dependence of the wave growth rate on the axial wavenumber and parameters of the plasma waveguide is studied. The results obtained in this paper are of interest for application in plasma electronics.

Synthesis of a Neutral Mononuclear Four-Coordinate Co(II) Complex Having Two Halved Phthalocyanine Ligands That Shows Slow Magnetic Relaxations under Zero Static Magnetic Field.

Syntheses of a novel pseudotetrahedral four-coordinate mononuclear Co(II) complex that has two halved phthalocyanine moieties as the ligands, [Co(half-Pc)2] (1), and its magnetic properties as a single molecule magnet (SMM) are reported. A one pot reaction of phthalonitrile and lithium methoxide followed by the coordination to a Co(II) ion gave 1 as an orange solid in a moderate yield. X-ray crystallography on 1 reveals tetragonally distorted coordination geometry around the Co(II) ion. The M- HT-1 plots suggest that 1 has large axial magnetic anisotropy. The ac magnetic susceptibility data of the magnetically diluted 1 (dil.1) clearly show that the complex acts as an SMM even in the absence of the external static magnetic field ( Hdc). The influence of intermolecular and intramolecular interactions for the magnetic relaxation behaviors has been discussed by comparison of the magnetic data of 1 and dil.1. The Orbach process is suggested as the predominant mechanism of magnetic relaxations in the high-temperature range, and the Arrhenius plots provide the effective relaxation energy barrier and pre-exponential factor of Ueff = 54.0 cm-1 and τ0 = 3.17 × 10-10 s, respectively. The direct estimation of the axial anisotropic parameter of 1 was successfully performed by high-field, multifrequency ESR measurements up to 55 T and 2.5 THz. The evaluated axial zero-field splitting (ZFS) energy of 57.0 cm-1 is comparable to the Ueff energy, confirming that the magnetic relaxations are initiated by the thermal excitation from the ground | M S⟩ = |±3/2⟩ states to the |±1/2⟩ states in the high-temperature range. The results of the ab initio calculations based on the CAS(7,5) SCF wave functions indicate that the ground states of 1 consist mainly of | M S⟩ = |±3/2⟩ states, while the first excited states are the mixture of | M S⟩ = |+1/2⟩ and |-1/2⟩.

Effect of magnetic field on absorption coefficients, refractive index changes and group index of spherical quantum dot with hydrogenic impurity

Optical properties of a spherical quantum dot (QD) with an on-center hydrogenic impurity in the external static magnetic field are studied. Energies and wavefunctions of the impurity electron are calculated using the Lagrange mesh method. Expressions for the optical absorption coefficients (ACs), refractive index changes (RICs) and group index (GI) are derived with the help of the density matrix formalism for a two-level system, and analyzed from the theoretical point of view. The behavior of ACs, RICs and GI with respect to the incident photon energy is examined, as well as their dependence on the magnetic field strength, laser intensity and relaxation time. It is observed that all of these parameters strongly affect the studied properties of the QD.

Nonthermal relativistic electron acceleration due to laser-induced incoherent wakefields with external static magnetic fields

Wakefield acceleration has been considered as a candidate of the origin of cosmic rays and the electron power-law spectra with an index of −2 and it has been demonstrated experimentally and numerically. In order to further support the universality of wakefield acceleration to address the power-law spectra of cosmic rays, we investigate the nonthermal acceleration of relativistic electrons due to the laser-induced wakefield acceleration with a static external magnetic field using two-dimensional particle-in-cell simulation.The results indicate that the power-law spectra with an index of −2 still remain even in the presence of external magnetic field.

Lossless and loss-induced topological transitions of isofrequency surfaces in a biaxial gyroelectromagnetic medium

Topological transitions of isofrequency surfaces of a composite magnetic-semiconductor structure influenced by an external static magnetic field are studied in the long-wavelength approximation. For the lossless case, the topological transitions of isofrequency surfaces from a closed ellipsoid to open Type I and Type II hyperboloids as well as a bi-hyperboloid are demonstrated. Conditions for critical points where the topological transitions occur are found out. It is revealed that actual material losses in the constituents of the composite medium strongly influence the dispersion behaviours for the extraordinary waves, which manifest themselves in the loss-induced topological transitions of isofrequency surfaces. It is shown that the loss-induced topological transitions from a Type I hyperboloid to a bi-hyperboloid appear in the frequency band where the real part of a particular principal component of the anisotropic constitutive parameter (permittivity or permeability tensor) is a near-zero value while its imaginary part is a non-zero value.

Poly-stable energy harvesting based on synergetic multistable vibration

Distributed energy sources, for example the ambient broadband vibrations, are of great importance for the development of the Internet of Things. However, for multistable vibrational energy harvesters, increasing the number of stable equilibrium states to broaden working frequency bands is very difficult. Here we present a poly-stable vibrational energy harvesting approach capable of achieving an exponentially growing maximum number of stable equilibrium states. Unlike the traditional multistable harvesters relying on an external static magnetic field, the nonlinear dynamical behaviours achieved by the proposed approach are synergetic poly-stable motions without the need of external magnets. Comparison experiments in contrast with a linear harvester demonstrate the working bandwidth widened by a factor of 41.0, the power density increased to 760% and the electricity generation raised to 178%. This demonstration of new multistable energy harvester expands the approach to achieving multistable motion and provides a new design philosophy for nonlinear vibrational energy harvesters.

Axion-electrodynamics: a quantum field calculation

An axion background field induces tiny oscillating electric and magnetic fields in an external static magnetic field. This signature is used to search for axion dark matter. We use standard quantum field theory techniques to obtain an expression for a transition amplitude, from which we identify the classical electromagnetic fields induced by the background axion field. We confirm previous results, that if the spatial size R of the applied static magnetic field is small compared to the axion Compton wavelength λ, the induced electric and magnetic fields are parametrically suppressed by the small numbers (R/λ)2 and R/λ, respectively, relative to the case when R is larger than λ. Our approach allows an intuitive interpretation in terms of 4-momentum conservation and momentum exchange via the photon propagator.

Electromagnetic energy rotation along plasma-metal interface in cylindrical waveguides initiated by azimuthal surface waves

Energy transfer along finite curvature plasma-metal interfaces in cylindrical metallic waveguides entirely filled by magnetoactive plasma is studied. Angular phase velocity, angular velocity of energy transfer, and angular group velocity are introduced and analyzed as functions of the waveguide parameters: radius, plasma particle density, azimuthal wave number, and external static axial magnetic field.

High-Sensitivity Three-Axis Vector Magnetometry Using Electron Spin Ensembles in Single-Crystal Diamond

We demonstrate a three-axis vector magnetometer based on ensembles of negatively charged nitrogen vacancy centers in single-crystal diamond. A diamond with $\text{C}_{3v}$ symmetry was used to establish the coordinate system for vector magnetic field sensing. We control the external static magnetic field with three-axis Helmholtz coils. Four pairs of magnetic resonance peaks were obtained, which were used to calculate the three Cartesian components of the magnetic field with sensitivity of $\sim5\;\text{nT}/ \sqrt{\text{Hz}}$ for each Cartesian component, free of interaxis error. The magnetometer is suitable for single-chip manufacturing.

Biological effects of static magnetic fields and zinc isotopes on E. coli bacteria.

The sensitivity of intracellular enzymatic systems to static magnetic fields (SMFs) and magnetic isotopes has been shown both in vitro and in vivo. These effects are determined by the spin-dependent magnetosensitive stages of enzymatic reactions. The search for experimental evidence of the combined effect of SMFs and zinc magnetic isotope 67 Zn on the intracellular processes on Escherichia coliEscherichia coli bacteria has taken place in vivo. The joint effects of external SMFs and magnetic zinc isotope 67 Zn on vital functions of E.coli bacteria have been shown experimentally. The combined effect of isotope 67 Zn and weak SMFs (25-35 mT) causes a 2-4-fold increase in the colony-forming ability and growth rate constants of bacteria E. coli compared with nonmagnetic zinc isotopes 64,66 Zn. The effects of SMFs in the range of 2.2-8 mT were detected for all bacteria, regardless of zinc isotope content in the media. An increase in ATP concentration in E. coli was detected for bacteria grown on a medium with the magnetic isotope 67 Zn in the SMF range of 2.2-4.2 mT. The major elements' (Na, K, Ca, Mg, P, Zn) metabolism in E. coli depend on the intensity of SMFs and zinc isotopes. These data confirm the existence of intracellular enzymatic processes stages that are sensitive to SMFs and magnetic moments of atomic nuclei. It is important to note that magnetic zinc 67 Zn and magnesium 25 Mg isotopes induce effects on viability of E. coli in different SMF ranges. Bioelectromagnetics. 40:62-73, 2019. © 2018 Wiley Periodicals, Inc.

Cutoff frequencies of accelerating modes propagation inside a cylindrical waveguide filled with radially inhomogeneous magnetized plasma

The cutoff frequencies of accelerating hybrid EH0l mode (l = 1, 2, 3, and 4) propagation are studied in a cylindrical waveguide filled with radially inhomogeneous plasma in the presence of an external static magnetic field applied along the waveguide axis. To drive the analytical cutoff equations, a model based on the Bessel-Fourier expansion, which considers strong spatial dispersion and a finite external magnetic field, is utilized. In order to examine the integrity of the cutoff equations, the well-known cutoff expression related to the hybrid EH wave in a homogeneous magnetized plasma waveguide is recalculated with the help of a new model. The cutoff equations are solved numerically, and the effects of the external magnetic field and plasma density are investigated on the cutoff frequencies of the EH0l modes (l = 1, 2, 3, and 4) in the particular waveguide with a radius of 2.1 cm. By studying the effect of the waveguide radius on the cutoff frequencies, it is revealed that the waveguide radius plays a decisive role in the behavior of the cutoff frequencies with the external static magnetic field and plasma density. It is found that a critical radius can be realized for the waveguide so that the cutoff frequency treatment with the external magnetic field and plasma density is reversed in it.

Study of the Effect of an External Magnetic Field on the Accuracy of NMRG

A theoretical model of nuclear magnetic resonance gyroscope (NMRG) has been established in this paper by the double noble gases in closed loop. The effect on the accuracy of NMRG by the external static magnetic field was analyzed. The fluctuation of the static magnetic field causes measurement error in the Earth’s rotary rate experiment. The atoms sense a constant magnetic field, when the fluctuation of the static magnetic field is compensated by the closed loop system. The results show that the Earth’s rotary rate measurement error decreases from 13.58 to 0.22°/h, which means 62 times, when the static magnetic field is compensated in closed loop. The fluctuation of the static magnetic field in the magnetic shield decreases 571 times. A higher accuracy of the NMRG is achieved when the fluctuation of the static magnetic field is effectively suppressed by the closed loop.

Born-Kuhn model for magnetochiral effects

This study focuses on theoretical and numerical investigations of the magnetochiral (MCh) effect in the optical region. Electrodynamics in a medium with broken time and space inversions is described by two orthogonal coupled oscillators, in what is known as the Born-Kuhn model, subject to an external static magnetic field. Constitutive equations and the refractive index of the medium are theoretically derived. The results show that the MCh effect is induced even in the absence of an intrinsic interaction between the magneto-optical effect and the optical activity. The study also numerically investigates the electromagnetic response in a metamaterial with magnetism and chirality in the deep ultraviolet region. The results agree well with the main results of our theory. This paper paves the way to realizing MCh metamaterials in the optical region.

Diode based on magneto-photonic crystals

Abstract The peculiarities of transmission and angular non-reciprocity in magneto-photonic crystals (MPC) are investigated. The problem of light transmission through magneto-photonic crystal is solved by Ambartsumian’s modified layer addition method. It is shown that the system under consideration can work as a wide band ideal optical diode for orthogonal circular polarizations and as a narrow band ideal optical diode for orthogonal linear polarizations. The influence of the magnitude of external static magnetic field, its direction, and the angle of incidence on the diode properties are investigated.

Resonance scattering of an extraordinary wave by a cylindrical density depletion in a magnetoplasma

Scattering of a normally incident extraordinary (Z mode) wave by a cylindrical density depletion aligned with an external static magnetic field in a magnetoplasma is studied. This problem is of importance for wave diagnostics of plasma density irregularities that can be formed under natural conditions of near-Earth space or during the modification of the ionosphere by high-power radio waves. The emphasis is placed on the behavior of scattering characteristics of the density depletion in the case where the frequency of the incident plane wave coincides with one of the resonant frequencies of such a plasma structure. The field patterns observed in the resonance scattering regimes are calculated and analyzed. The results obtained can be helpful in understanding the basic properties of resonance scattering of electromagnetic waves from the field-aligned density irregularities and planning the related ionospheric and laboratory experiments.

The effect of static external magnetic field on the nonlinear absorption of the S-polarised short laser pulse in collisional underdense plasma

Inverse Bremsstrahlung absorption is a mechanism for generating heat in the inertial confinement fusion (ICF) process. To maximise the heat produced, it is desirable to investigate the possibilities for increasing the absorption rate through the inverse Bremsstrahlung process. It should be noted that some absorption mechanisms found for nanosecond long laser pulses also appear for ultrashort laser pulses. In this paper, the physics of absorption for S-polarised laser pulse and magnetised underdense plasma interaction in the presence of electrons ohmic heating and ponderomotive nonlinearities is analysed for both collisional isothermal and collisional non-isothermal magnetised plasmas. Here, we show that, in the presence of a static magnetic field, the absorption rate of the S-polarised laser pulse through interaction with underdense plasma can be increased intensively. In other words, by applying an external magnetic field, the laser pulse radiation will penetrate a region of greater plasma density compared to the case of non-magnetised plasma for the S-polarised absorption. It is remarkable that due to the heat of the plasma at the expanse of the wave energy in the case of the non-thermal, magnetised and collisional plasma, the absorption coefficient is increased intensively in comparison with the collisional plasma.