Magnetic Dipole Contributions Research Articles

Performance of Magnetic Dipole Contribution on Electromagnetic Ellis Tetra Hybrid Nanofluid with the Applications of Surface Tension Gradient: A Xue Model Exploration

Performance of Magnetic Dipole Contribution on Electromagnetic Ellis Tetra Hybrid Nanofluid with the Applications of Surface Tension Gradient: A Xue Model Exploration

Toroidal mode trapping in a magnetic meta-molecule

Abstract In this paper, we establish the relationship between the eigenmodes and the scattering characteristics of a meta-molecule made of magnetic disks from the point of view of the manifestation of its toroidal response. In particular, we examine the electric and magnetic dipole contributions to the scattering cross-sections obtained in the framework of the multipole decomposition method while accounting for the polarizability and magnetization induced in the structure by the field of incoming radiation. We find out that with increasing permeability, the toroidal mode is trapped in the meta-molecule due to the presence of its magnetization part, which may have a practical perspective in gyrotropy, permittivity, and permeability sensing.

Inverse Faraday Effect in Ferrite–Garnet Films in the Near-Infrared Range

The magneto-optical Faraday effect is determined by the electric dipole and magnetic dipole transitions in a transparent magnetic material. At the same time, the inverse Faraday effect is still described by an expression that includes only electric dipole transitions. The magnetic dipole contribution to the inverse Faraday effect is considered theoretically, and the dependence of the inverse Faraday effect on the wavelength in the near-infrared range (where the magnetic dipole contribution becomes significant) is obtained by the example of a ferrite–garnet film. It is shown that, although both contributions to the inverse Faraday effect always take place for homogeneous films, only the magnetic-dipole inverse Faraday effect manifests itself for films with a periodic nanostructure upon excitation by a TE waveguide mode, which may be useful for its experimental observation.

Broadband nonreciprocal gyromagnetic metasurface via magnetic Kerker-type dimers

Optical nonreciprocity, stemming from the deviation of the Lorentz reciprocity theorem, holds significant interest in the realm of optics and electromagnetics. Here, we propose and experimentally demonstrate broadband nonreciprocal transmission via a low-biased magnetic Kerker-type dimer metasurface. The designed magneto-optical metasurface comprises three layers of metal sandwiched between two gyromagnetic near-zero thickness slabs. The Kerker-type dimers broaden the isolation bandwidth utilizing multiple resonances where the double-stacked metallic disks act as Kerker-type dipoles, enhancing the transmissibility of the metasurface. The multipole decomposition reveals that the magnetic dipole contribution arising from magnetization is the primary cause of the metasurface's nonreciprocal response. Microwave measurement demonstrates that the bandwidth for an isolation ratio exceeding 10 dB is over 3 GHz. The broadband nonreciprocal performance remains relatively stable, exhibiting strong robustness against the bias disturbance. Our findings provide an alternative avenue for enhancing broadband nonreciprocity transmission under a low-biased magnetic field.

Magneto-plasmonic scattering by a disk-shaped particle made of an artificial dielectric

The main features of artificial dielectrics are high anisotropy and controllable heterogeneity, as well as adjustable values of their synthesized material parameters. In this work, we numerically study the scattering features of a disk-shaped particle made of an artificial dielectric (finely stratified structure, FSS) that is composed of magnetic and semiconductor constituents influenced by an external static magnetic field. The tensor-valued permittivity and permeability of the FSS are derived involving the effective medium theory. Due to a specific composition of the FSS, the material properties of the disk simultaneously acquire electric and magnetic gyrotropy, which depends on the proportion of the semiconductor and magnetic components included in the FSS. It is supposed that the ferromagnetic and plasma resonances of the constitutive materials are closely spaced. In particular, we examine the electric and magnetic dipole contributions to the scattering and absorption cross-sections obtained in the framework of the multipole decomposition method while accounting for the polarizability and magnetization induced in the particle by the field of incoming radiation. By varying the proportion of components of the artificial dielectric, we demonstrate the magneto-plasmonic functionality of the particle. Our presentation generalizes and complements several known solutions obtained separately for either magnetic or dielectric anisotropic particles. This approach can be used to study magneto-optical effects in metamaterials and metasurfaces composed of an ensemble of gyroelectric and gyromagnetic particles that is important for both plasmonic and photonic applications.

Study of weak magnetism by precision spectrum shape measurements in nuclear beta decay

Nuclear beta decays play an important role in uncovering the nature of the weak interaction. The weak magnetism (WM) form factor, b WM, is generally a small correction to the beta decay rate that arises at first order as an interference term between the dominant Gamow-Teller and the magnetic dipole contributions to the weak current. This form factor is still poorly known for nuclei with higher atomic number. We performed a careful analysis of the measured beta spectrum shape for Gamow-Teller transitions in 114In and 32P nuclei. The precision spectrum shape measurements were carried out using the miniBETA spectrometer consisting of a low-mass, low-Z multi-wire gas tracker and a plastic scintillator energy detector. The preliminary results for the weak magnetism extraction for 114In and 32P nuclei are presented.

Impact of magnetic dipole contribution on radiative ferromagnetic Cross nanofluid flow with viscous dissipation aspects

Due to the broad range of applications of nanofluid in engineers, the researchers are paying attention toward them as an innovative fluid having unique features as compared to conventional fluids. Furthermore, the purpose of current work is to explore the initial working of 2D ferrofluid flow passing over a moving sheet with effects of magnetic dipole. Cross fluid model is under discussion along with ferrofluids which have been studied with focus on heat and mass transfer, including thermophoresis and Brownian motion effects. The particular flow design was preferred because of its common use in numerous fields such as biomedicine and engineering. In this paper, the effects of magnetic dipoles as well as thermal radiation for stretching surface in ferromagnetic fluids flow are deliberated. This study investigates the nonlinear ODE by using some appropriate similarity transformations then obtained ODEs were numerically analyzed using a numerical scheme of bvp4c. Effects of ferromagnetic relation coefficients, Curie temperature, viscous dissipation, Weissenberg number, impacts of thermal radiation on the velocity, temperature and concentration is also under discussion. In addition, thermal gradients, velocities, as well as mass transfer rates are carefully observed pictorially and certain results are concluded. The major findings of this study depend on the consequence of control parameters on thermal field, momentum and concentration. It is observed that the temperature of the magneto-fluid increases for higher values of the FHD interaction as well as Curie temperature parameters. The concentration distribution of ferrofluid represents an opposite trend for thermophoresis and Brownian motion.

Nonreciprocity of Optical Absorption in the Magnetoelectric Antiferromagnet CuB2O4

The change in the absorption spectra due to reversal of the direction of light propagation (nonreciprocity of absorption) is a consequence of a simultaneous violation of both time-reversal and spatial-inversion symmetries. Here, we report on a high-resolution spectroscopic study of absorption nonreciprocity in the noncentrosymmetric multiferroic CuB2O4 below the antiferromagnetic transition temperature TN = 21 K in the commensurate phase in magnetic fields up to 0.5 T. The study was performed in a broad spectral region covering several exciton transitions, which all are followed by an anomalously rich structure due to the multiple exciton-magnon-phonon satellites. Two components were resolved for the spectral line near 1.4 eV corresponding to the exciton transition between the ground and the first excited state. A quantitative theory of the optical absorption and nonreciprocity at this line was developed. The theory takes into account the interference between the electric and magnetic dipole contributions to the absorption and gives an adequate explanation of the relevant effects.

Performance of magnetic dipole contribution on ferromagnetic non-Newtonian radiative MHD blood flow: An application of biotechnology and medical sciences

Casson flow ferromagnetic liquid blood flow over stretching region is studied numerically. The domain is influence by radiation and blood flow velocity and thermal slip conditions. Blood acts an impenetrable magneto-dynamic liquid yields governing equations. The conservative governing nonlinear partial differential equations, reduced to ODEs by the help of similarity translation technique. The transport equations were transformed into first order ODEs and the resultant system are solved with help of 4th order R-K scheme. Performing a magnetic dipole with a Casson flow across a stretched region with Brownian motion and Thermophoresis is novelty of the problem. Significant applications of the study in some spheres are metallurgy, extrusion of polymers, production in papers and rubber manufactured sheets. Electronics, analytical instruments, medicine, friction reduction, angular momentum shift, heat transmission, etc. are only few of the many uses for ferromagnetic fluids. As ferromagnetic interaction parameter value improves, the skin-friction, Sherwood and Nusselt numbers depreciates. A comparative study of the present numerical scheme for specific situations reveals a splendid correlation with earlier published work. A change in blood flow velocity magnitude has been noted due to Casson parameter. Increasing change in blood flow temperature noted due to Casson parameter. Skin-friction strengthened and Nusselt number is declined with Casson parameter. The limitation of current work is a non-invasive magnetic blood flow collection system using commercially available magnetic sensors instead of SQUID or electrodes.

Strong Er3+ radiative emission enhancement by quasi-BIC modes coupling in all-dielectric slot nanoantenna arrays

We have designed and realized all-dielectric lossless nanoantennas, in which a thin SiO2 layer doped with erbium ions is placed inside slotted silicon nanopillars arranged in a square array. The modal analysis has evi-denced that the slotted nanopillar array supports optical quasi-BIC resonances with ultra-high Q-factors (up to Q∼109), able to boost the electromagnetic local density of optical states in the optically active layer. Up to 3 orders of magnitude photoluminescence intensity increment and 2 orders of magnitude decay rate enhancement have been measured at room temperature when the Er3+ emission at about λ=1540 nm couples with the quasi-BIC resonances. Furthermore, by tailoring the nanopillar aspect ratio, the slot geometry has been exploited to obtain selective enhancements of the electric or magnetic dipole contribution to Er3+ radiative transitions in the NIR, keeping the emitter quantum efficiency almost unitary. Finally, by computing the angularly resolved elec-tromagnetic field enhancement inside the nanoslot, the nanoantenna directivity has been designed, proving that strong beaming effects can be obtained. Our findings have a direct impact on the development of bright and effi-cient photon sources operating at telecom wavelength that are of primary importance for quantum nanophotonic applications.

Subcycle-resolved strong-field tunneling ionization: Identification of magnetic dipole and electric quadrupole effects

Interaction of a strong laser pulse with matter transfers not only energy but also linear momentum of the photons. Recent experimental advances have made it possible to detect the small amount of linear momentum delivered to the photoelectrons in strong-field ionization of atoms. Linear momentum transfer is a unique signature of the laser-atom interaction beyond its dipolar limit. Here, we present a decomposition of the subcycle time-resolved linear momentum transfer in term of its multipolar components. We show that the magnetic dipole contribution dominates the linear momentum transfer during the dynamical tunneling process while the post-ionization longitudinal momentum transfer in the field-driven motion of the electron in the continuum is primarily governed by the electric quadrupole interaction. Alternatively, exploiting the radiation gauge, we identify nondipole momentum transfer effects that scale either linearly or quadratically with the coupling to the laser field. The present results provide detailed insights into the physical mechanisms underlying the subcycle linear momentum transfer induced by nondipole effects.

Trade‐Off between Second‐ and Third‐Order Nonlinearities, Ultrafast Free Carrier Absorption and Material Damage in Silicon Nanoparticles

AbstractReaching the optimal second‐ and third‐order nonlinear conversion efficiencies while avoiding undesirable free carrier absorption losses and material damage in ultrashort laser‐excited nanostructures is a challenging obstacle in all‐dielectric ultrafast nanophotonics. In order to elucidate the main aspects of this problem, a multi‐physical model is developed, coupling nonlinear Maxwell equations supplied by surface and bulk nonlinearities with free carrier hydrodynamic equations for electron–hole plasma kinetics and electron‐ion transfer for silicon. The maximum feasible efficiencies for a single spherical particle supporting different electric and magnetic resonances are compared, and the harmonic yields are further optimized by tuning lattice resonances in a periodic arrangement of nanoparticles. Results support the dominant role of magnetic dipole and quadrupole contributions in the enhancement of the third harmonic and the electric dipole for the second harmonic, as well as the possibility to further improve the conversion of both harmonics simultaneously at least by two orders of magnitude by designing properly the resonant metasurface.

The quasi bound spectrum of H2

We compute the radiative ro-vibrational emission spectrum of H involving quasi-bound states via a simple numerical method of resolution of the Schrödinger equation by introducing a modified effective molecular potential. The comparison of the eigenvalues obtained with our approximation and other theoretical methods based on scattering resonance properties is excellent. Electric quadrupole and magnetic dipole contributions are calculated and we confirm the previous computations of Forrey of the electric quadrupole transition Einstein coefficients. The astrophysical relevance of such quasi-bound levels is emphasized.

Spectroscopic investigation of dysprosium doped bismuth-borate glasses for white light application

In this work, the spectroscopic properties of Dysprosium doped lithium-bismuth-borate glasses were investigated for different photonic and lasing applications. The photon absorption was observed in Uv–Vis–NIR region. Using Jud-Ofelt analysis the electric and magnetic dipole contribution were calculated to determine the parameters (Ω = 2, 4, 6), radiative lifetime and branching ratios of BBiLDy15 glass. The visible luminescence spectra at 482, 576, 663 and 772-nm correspond to transitions 4F9/2 → 6HJ (J = 15/2, 13/2, 11/2, 9/2) under λex = 350 nm were observed. The lasing parameters like stimulated emission cross section (5.45 × 10−22 cm2) and experimental branching ratio (61%) of the BBiLDy1.5 glass were determined from the visible transitions in the PL-emission spectra. The decrease in life time value of glass samples was observed that was attribute to the energy transfer via resonance energy transfer (RET) from host matrix to luminescence centers. The CIE chromaticity color co-ordinates, CCT results and the emission cross section for the visible transitions emphasizing the capacity of BBiLDy glass samples as potential material for white light emitting diodes and visible laser application.

Nuclear magnetic relaxation studies of BH4 in metal Borohydrides

AbstractA different approach of nuclear magnetic resonance (NMR) relaxation of the rotational motion of BH4 tetrahedron in light metal borohydrides was introduced. Previous NMR relaxation studies were mainly performed using an approximation which is based on a single exponential transition approach for the spin–lattice relaxation of the spin under quadrupolar interaction. In this new approach, a relaxation rate equation was derived by strictly taking into account both electric quadrupolar and magnetic dipolar contributions to the transitions between Zeeman energy states of quadrupolar 11B nucleus that was coupled to many proton spins. Two exponential relaxation times derived from our theoretical treatment were applied to the analysis of 11B spin–lattice relaxation of LiBH4 and Ca(BH4)2. The activation energies and the correlation times of the reorientational motions of BH4 were evaluated from the two experimental spin–lattice relaxation times. The results were compared to previous activation energies and correlation times.

Searching for Magnetic Monopoles with Earth's Magnetic Field.

Magnetic monopoles have long been predicted in theory and could exist as a stable object in our Universe. As they move around in galaxies, magnetic monopoles could be captured by astrophysical objects like stars and planets. Here, we provide a novel method to search for magnetic monopoles by detecting the monopole moment of Earth's magnetic field. Using over six years of public geomagnetic field data obtained by the Swarm satellites, we apply Gauss's law to measure the total magnetic flux, which is proportional to the total magnetic charge inside Earth. To account for the secular variation of satellite altitudes, we define an altitude-rescaled magnetic flux to reduce the dominant magnetic dipole contribution. The measured magnetic flux is consistent with the existing magnetic field model that does not contain a monopole moment term. We therefore set an upper limit on the magnetic field strength at Earth's surface from magnetic monopoles to be |B_{m}|<0.13 nT at 95%confidence level, which is less than 2×10^{-6} of Earth's magnetic field strength. This constrains the abundance of magnetically charged objects, including magnetic black holes with large magnetic charges.

Electric-quadrupole and magnetic-dipole contributions to the ν2+ν3 band of carbon dioxide near 3.3 µm

The recent detections of electric-quadrupole (E2) transitions in water vapor and magnetic-dipole (M1) transitions in carbon dioxide have opened a new field in molecular spectroscopy. While in their present status, the spectroscopic databases provide only electric-dipole (E1) transitions for polyatomic molecules (H2O, CO2, N2O, CH4, O3…), the possible impact of weak E2 and M1 bands to the modeling of the Earth and planetary atmospheres has to be addressed. This is especially important in the case of carbon dioxide for which E2 and M1 bands may be located in spectral windows of weak E1 absorption. In the present work, a high sensitivity absorption spectrum of CO2 is recorded by Optical-Feedback-Cavity Enhanced Absorption Spectroscopy (OFCEAS) in the 3.3 µm transparency window of carbon dioxide. The studied spectral interval corresponds to the region where M1 transitions of the ν2+ν3 band of carbon dioxide were recently identified in the spectrum of the Martian atmosphere. Here, both M1 and E2 transitions of the ν2+ν3 band are detected by OFCEAS. Using recent ab initio calculations of the E2 spectrum of 12C16O2, intensity measurements of five M1 lines and three E2 lines allow us to disentangle the M1 and E2 contributions. Indeed, E2 intensity values (on the order of a few 10–29 cm/molecule) are found in reasonable agreement with ab initio calculations while the intensity of the M1 lines (including an E2 contribution) agree very well with recent very long path measurements by Fourier Transform spectroscopy. We thus conclude that both E2 and M1 transitions should be systematically incorporated in the CO2 line list provided by spectroscopic databases.

Constructive and destructive interference of Kerker-type scattering in an ultrathin silicon Huygens metasurface

High refractive index dielectric nanoparticles have provided a new platform for exotic light manipulation through the interference of multipole modes. The Kerker effect is one example of a Huygens source design. Rather than exploiting interference between the electric dipole and magnetic dipole, as in many conventional Huygens source designs, we explore Kerker-type suppressed backward scattering mediated by the dominant electric dipole, toroidal dipole and magnetic quadrupole. These modes are provided by a designed and fabricated CMOS compatible ultra-thin Silicon nanodisk metasurface with a suppressed magnetic dipole contribution, and verified through multipole decomposition. The non-trivial substrate effect is considered using a semi-analytical transfer matrix model. The model successfully predicts the observed reflection dip. By applying a general criterion for constructive and destructive interference, it is shown that while constructive interference occurs between the electric and toroidal dipole contributions, the experimentally observed suppressed backward Kerker-type scattering arises from the destructive interference between backward scattered contributions due to the total electric dipole and the magnetic quadrupole. Our study paves the way towards new types of Huygens sources or metasurface design, such as for peculiar transverse Kerker scattering.

Circular dichroism second-harmonic generation microscopy probes the polarity distribution of collagen fibrils

Second-harmonic generation (SHG) microscopy is currently the preferred technique for visualizing collagen in intact tissues, but the usual implementations struggle to reveal collagen fibrils oriented out of the imaging plane. Recently, an advanced SHG modality, circular dichroism SHG (CD-SHG), has been proposed to specifically highlight out-of-plane fibrils. In this study, we present a theoretical analysis of CD-SHG signals that goes beyond the electric dipolar approximation to account for collagen chirality. We demonstrate that magnetic dipolar contributions are necessary to analyze CD-SHG images of human cornea sections and other collagen-rich samples. We show that the sign of CD-SHG signals does not reveal whether collagen fibrils point upwards or downwards as tentatively proposed previously. CD-SHG instead probes the polarity distribution of out-of-plane fibril assemblies at submicrometer scale, namely homogeneous polarity versus a mix of antiparallel fibrils. This makes CD-SHG a powerful tool for characterizing collagen organization in tissues, specifically the degree of disorder, which is affected during pathological remodeling. CD-SHG may thus serve to discriminate healthy and diseased collagen-rich tissues.

Study on an application manner of Judd-Ofelt theory to a phosphor material

Abstract An application manner of Judd-Ofelt (J-O) theory to a luminescent powder is studied by exemplifying an Er3+-doped Li5La3Nb2O12 nanophosphor, on which J-O analysis has been performed previously using the approach based on measured relative absorption (optical density) spectrum and Er3+ 1.5 μm fluorescence lifetime. Present study focuses on two key issues that are closely related to the reliability and application manner of the approach but not clarified in the previous study. First, whether or not a strong or medium-intensity oscillator, such as the 4I15/2↔4I13/2 (1.5 μm) one, can be excluded from the J-O least-square fit. Second, whether the relative ratio between the J-O intensity parameters Ωi (i = 2, 4, 6) remains unchanged as the integrated optical densities (IODs) of all transitions change all together by a factor x. Our studies show that the strong or medium-intensity transition oscillator, such as the 4I15/2↔4I13/2 one, must be included in the J-O fit. The relative ratios between Ωi change remarkably with the collectively varying factor x of the IODs for smaller x values because of magnetic dipole contribution of the 1.5 μm oscillator. The change is undesired as it may result in the deviation of Ωi values, and hence restricts the application manner of the related approach. A more reliable application manner of the approach is proposed.