Magnetic Dipole Research Articles

Enhancing Antireflection Based on a Symmetry-Dependent Kerker Effect.

The significance of antireflection has persisted over time due to its numerous optical applications. To achieve broadband antireflection, multiple element-based designs using graded-index films or multiresonant nanostructures have been conventionally employed. In this work, we propose an additional degree of freedom in developing antireflection by manipulating the orientation angles of nanostructures to achieve the symmetry-dependent Kerker condition. Under the excitation of multipoles in higher-order resonances, which typically complicates the interference condition, the perfect Kerker condition is demonstrated without backward leakage of power at a wavelength significantly shorter than the excitation bandwidth of electric and magnetic dipoles. Such a condition can be directly linked to the symmetry of resonators and maximized by suppressing the near-field coupling and optimizing polarization-related spatial parities. We experimentally demonstrate the symmetry-dependent Kerker condition and polarization-independent antireflection at the midwave infrared range, which has attracted increasing attention in emerging imaging and sensing fields.

Repercussions of thermally stratified magnetic dipole for mixed convectively heated Darcy-Forchheimer Carreau-Yasuda nanofluid flow via viscous dissipation analysis

Nowadays nanotechnology is progressing speedily with the passage of time, consequently the research on innovative fluid termed as nanofluid is at its peak. Invention of nanofluid has made a revolution in engineering and chemical processes due to its enhanced heat transmission characteristics along with environmental friendliness as well as financially affordability of nanofluid are causes of its attraction among the research community. In current study the basic aim is to scrutinize a rheological ferrofluid model with magnetic effects. The procedure for conversion of coupled P.D. Es into coupled set of O.D.Es which is performed by use of similarity variables. The numerical scheme used here is bvp4c scheme for obtaining the required numerical outcomes. A comprehensive review of graphical illustration for fluid's temperature, velocity as well as concentration is delivered here. We inspected that with upsurge of parameter for Brownian motion resultantly concentration of fluid declines while increase in thermal profile is noted.

Magnetic manipulation of unknown and complex conductive nonmagnetic objects with application in the remediation of space debris

This article extends recent work in magnetic manipulation of conductive, nonmagnetic objects using rotating magnetic dipole fields. Eddy-current-based manipulation provides a contact-free way to manipulate metallic objects. We are particularly motivated by the large amount of aluminum in space debris. We previously demonstrated dexterous manipulation of solid spheres with all object parameters known a priori. This work expands the previous model, which contained three discrete modes, to a continuous model that covers all possible relative positions of the manipulated spherical object with respect to the magnetic field source. We further leverage this new model to examine manipulation of spherical objects with unknown physical parameters by applying techniques from the online-optimization and adaptive-control literature. Our experimental results validate our new dynamics model, showing that we get improved performance compared to the previously proposed model, while also solving a simpler optimization problem for control. We further demonstrate the first physical magnetic manipulation of aluminum spheres, as previous controllers were only physically validated on copper spheres. We show that our adaptive control framework can quickly acquire useful object parameters when weakly initialized. Finally, we demonstrate that the spherical-object model can be used as an approximate model for adaptive control of nonspherical objects by performing magnetic manipulation of a variety of objects for which a spherical model is not an obvious approximation.

CPT-Odd effects on the electromagnetic properties of charged leptons in the Standard Model Extension

Abstract The impact of the CPT-Odd electroweak gauge sector of the Standard Model Extension on the magnetic dipole moment of charged leptons is studied. This gauge sector is characterized by the (k1)µ and (k2)µ Lorentz coefficients, which have positive mass dimension because they are associated with a UY (1)-invariant and with an SUL(2)-invariant dimension-three operators, respectively. They belong to the category of relevant interactions, which have strong effects on low-energy observables. We present a comprehensive study on the impact of this sector on the magnetic dipole moment of charged leptons, up to second order in these Lorentz coefficients, both at the tree and one-loop levels. We find that the first-order contributions in the Lorentz coefficients at the tree and one-loop levels depend on energy, while second-order ones at the tree-level do not. As for second-order one-loop effects, there are both energy-dependent and energy-independent contributions, but we have focused only on those of the latter type. We find that the tree-level contributions are suppressed with respect to the one-loop ones by at least a factor of (m2l /m2Z). We find that the contribution to the dipole associated with the electron is by far the dominant one, as it can be up to fourteen orders of magnitude greater than that of the muon and up to sixteen orders greater than that of the tau. The Lorentz coefficient (kAF )µ of the Carroll-Field-Jackiw’s QED is given by a linear combination of the (k1)µ and (k2)µ vectors. Assuming thatcollinear, we obtain an upper bound of|k12|,|k22| ≫ |k2AF| and taking (kAF)µ = 0, which implies that (|||−(3.49 × 10-4)(k2)0me + k2 | k1)µ and (k2)µ are.

Inversion of circularly polarized luminescence by electric current flow during transition.

The development of chiral compounds exhibiting circularly polarized luminescence (CPL) has advanced remarkably in recent years. Designing CPL-active compounds requires an understanding of the electric transition dipole moment (μ) and the magnetic transition dipole moment (m) in the excited state. However, while the direction and magnitude of μ can, to some extent, be visually inferred from chemical structures, m remains elusive, posing challenges for direct predictions based on structural information. This study utilized binaphthol, a prominent chiral scaffold, and achieved CPL-sign inversion by strategically varying the substitution positions of phenylethynyl (PE) groups on the binaphthyl backbone, while maintaining consistent axial chirality. Theoretical investigation revealed that the substitution position of PE groups significantly affects the orientation of m in the excited state, leading to CPL-sign inversion. Furthermore, we propose that this CPL-sign inversion results from a reversal in the rotation of instantaneous current flow during the S1 → S0 transition, which in turn alters the orientation of m. The current flow can be predicted from the chemical structure, allowing anticipation of the properties of m and, consequently, the characteristics of CPL. This insight provides a new perspective in designing CPL-active compounds, particularly for C2-symmetric molecules where the S1 → S0 transition predominantly involves LUMO → HOMO transitions. If μ represents the directionality of electron movement during transitions, i.e., the "difference" in electron locations before and after transitions, then m could be represented as the "path" of electron movement based on the current flow during the transition.

Closed-form expressions for magnetic polarizabilities of circular apertures excited by nonuniform magnetic fields

Abstract The problem of electromagnetic penetration through an aperture in a perfectly electrically conducting plane is a classical problem in electromagnetic theory and applications. This work aims to investigate the behavior of an electrically small aperture when excited by nonuniform magnetic fields. Based on the Taylor expansion of the exact solution in integral form of the corresponding mixed boundary problem, we derive the equivalent magnetic dipole moment of a circular aperture. Closed-form expressions of dipole moments are derived. Also, for the special case of axisymmetric excitation where the dipole moment vanishes, we develop a quadrupole model to describe the aperture behavior. The effectiveness of the obtained expressions is verified by comparisons with accurate analytical solutions in special cases and the exact solutions in integral form.

Nonrelativistic ferromagnetotriakontadipolar order and spin splitting in hematite

We show that hematite, α−Fe2O3, below its Morin transition, has a ferroic ordering of rank-5 magnetic triakontadipoles on the Fe ions. In the absence of spin-orbit coupling, these are the lowest-order ferroically aligned magnetic multipoles, and they give rise to the g-wave nonrelativistic spin splitting in hematite. We find that the ferroically ordered magnetic triakontadipoles result from the simultaneous antiferroic ordering of the charge hexadecapoles and the magnetic dipoles, providing a route to manipulating the magnitude and the sign of the magnetic triakontadipoles as well as the spin splitting. Furthermore, we find that both the ferroic ordering of the magnetic triakontadipoles and many of the spin-split features persist in the weak ferromagnetic phase above the Morin transition temperature. Published by the American Physical Society 2024

Review of: "Magnetic dipoles in paramagnetic material do not have specific and regular orientation; as a result, these materials do not have magnetic properties"

Review of: "Magnetic dipoles in paramagnetic material do not have specific and regular orientation; as a result, these materials do not have magnetic properties"

High gain nested dielectric resonator rectenna based on higher order mode and magneto-electric dipole theory

In this paper, a high-gain nested dielectric resonator rectenna operating at 5.8 GHz based on the magneto-electric dipole theory is proposed. A nested structure is employed to achieve the required resonant frequency in a small dimension. And the higher order HE21δ mode of the dielectric resonator antenna (DRA) is excited by a vertical coaxial probe feeding, which is equated to a horizontal array of crossed magnetic dipoles, thus enhancing the gain. Then, two vertical metal posts are embedded inside the DRA, serving as electric dipoles to form a magneto-electric dipole array in conjunction with the magnetic dipoles, which suppress the excessive lobes of the DRA in HE21δ mode and hence enhance the maximum gain of the DRA to 9.8 dBi. A rectifier circuit with harmonic suppression is designed. By adding a short-circuit microstrip transmission line to the rectifier circuit, the second harmonic with infinite impedance is suppressed and reflected back to the diode for secondary rectification. The designed rectifier circuit is connected to the DRA to form a rectenna. The test result shows that the rectenna obtains a peak conversion efficiency of 43.9 % and an output voltage of 1.95 V at 5.8 GHz, which is suitable for wireless energy harvesting.

Demonstration of Magnetic Dipole–Dipole Interaction Using a Smartphone Pressure Sensor

Demonstration of Magnetic Dipole–Dipole Interaction Using a Smartphone Pressure Sensor

Multiple surface lattice resonances in symmetric nanocuboid dimer arrays

Abstract Surface lattice resonances based on nanoparticle arrays have significant characteristics such as localized field enhancement and high quality factor, and can be applied in fields such as optical sensors and lasers. In this work, we propose a symmetric Si/SiO2 nanocuboid dimer array that can generate and regulate two surface lattice resonances. One of the surface lattice resonances (named SLR1) is mainly due to the coupling between the electric dipole resonance of single Si/SiO2 nanocuboid dimers and the diffraction waves perpendicular to the applied electric field. Another surface lattice resonance (named SLR2) mainly originates from the coupling between the magnetic dipole resonance of single Si/SiO2 nanocuboid dimers and the diffraction waves parallel to the direction of the applied electric field. The research results indicate that the polarization direction of the incident field, the period of the array, the gap between the nanocuboids in the dimer, particle size, and the medium environment are all important for regulating the two surface lattice resonances. The sensing application of multiple surface lattice resonances is also investigated. The results show that under appropriate structural parameters, SLR1 can provide good stability for sensing applications, its sensitivity and figures of merit are 472 nm RIU−1 and 104, respectively. However, SLR2 is very weak or suppressed when the refractive index of the medium environment is greater than or equal to 1.2. This characteristic limits the application range of SLR2 in sensing. This work is of great significance for the design of micro-nano photonic devices based on multiple surface lattice resonances.

Structural design and test of superconducting magnet coil for the cooling storage ring external-target experiment

Abstract Heavy ion collision is an unique method for studying cold and dense nuclear matter in labs. The Cooling Storage Ring (CSR) External-target Experiment (CEE) at the Heavy Ion Research Facility in Lanzhou (HIRFL), China, is the first multi-purpose nuclear physics experimental device to operate in the GeV energy range. One of the key parts is a large acceptance dipole magnet, which is used to bend particles so that they can be detected by various detectors. A superconducting coil with the size of 3.1 m ×3.6 m × 2 m was designed to verify the rationality of the scheme. Although the coil-dominated superconducting magnet with NbTi has been used to reduce the weight and size of the magnet, large deformation and stress will occur in the cooldown and excitation stages owing to the large volume and weight. Therefore, it is crucial to design a reasonable structure to ensure the strength of the magnet and prevent the magnet from interfering with other components due to large deformation, and even the possibility of quenching. A truss supporter is proposed for the support of the superconducting coil. In this study, the structural design of the cold mass of a superconducting magnet is introduced, and its mechanical behaviors during cooldown and excitation are analyzed in detail. To verify the feasibility of the coil design and process route, a sub-size prototype was manufactured and tested at 4.2 K and reached the design current successfully.

Low-profile pattern reconfigurable patch antenna with dual bands characteristic for 5G NR communication

Abstract In this paper, a low-profile antenna with characteristic of reconfigurable of dual bands’ pattern for 5G New Radio (NR) communication is proposed to mitigate the problems of signal fading and multipath propagation. The design incorporates a turnstile-shaped patch, a circular patch with etched rectangular slots and a discontinuous ring patch. The circular patch with etched rectangular slots and discontinuous ring patch are placed in the same plane to obtain dual band characteristic. The discontinuous ring patch works as a near-field resonant parasitic unit to improve the front-to-back ratio values at the resonance points and adjust the beam direction. Eight diodes are loaded to control the connection states of the rectangle slots on the circular patch. By combining an electric dipole formed by diode-controlled slot with a magnetic dipole formed by the turnstile-shaped patch, then a dual-band antenna with diverse patterns is designed. The measured results show that the designed antenna has dual-band characteristics and operates in the bands of 3.39–3.62 GHz and 4.77–5.01 GHz with peak gains of 3.6 dBi and 4.2 dBi, respectively. Furthermore, the measured radiation pattern results show that it is feasible to reconfigure the pattern in both bands simultaneously at 45° intervals.

Fe-loaded two-dimensional nitrogen-doped carbon for electromagnetic wave absorption

Abstract Electromagnetic wave absorbing materials are particularly important in modern electronics, especially in the fields of stealth and communications. Carbon-based materials show great promise in the production and application of efficient wave-absorbing materials due to their rich structure, ultra-light weight, good corrosion resistance, and low cost. Among them, nitrogen-doped carbon-based two-dimensional materials have a stronger depletion effect on electromagnetic waves due to their higher specific surface area and abundant polarization states. In this article, nitrogen-doped carbon 2D flakes (NC) were successfully synthesized by a hydrothermal method. Furthermore, Fe single atoms were successfully loaded onto their surfaces, creating Fe@NC. The wave-absorbing properties of Fe@NC samples were significantly enhanced, with the minimum reflection loss (RLmin) reaching -69.22 dB at 11.48 GHz and the effective absorption bandwidth (EAB) extending to 5.79 GHz. The enhancement of electromagnetic wave absorption is attributed to the synergistic effects of magnetic loss, relaxation processes, dipole polarization, and electrical conduction loss. The successful preparation of Fe@NC offers new possibilities for the development of atomically dispersed wave-absorbing materials.

Magnetic Monopole Phenomenology at Future Hadron Colliders

Abstract In the grand tapestry of Physics, the magnetic monopole (MM) is a holy grail. Therefore, numerous efforts are underway in search of this hypothetical particle at CMS, ATLAS, and MoEDAL experiments of Large Hadron Collider (LHC) by employing different production mechanisms. The cornerstone of our comprehension of monopoles lies in Dirac’s theory which outlines their characteristics and dynamics. Within this theoretical framework, an effective U(1) gauge field theory, derived from conventional models, delineates the interaction between spin magnetically-charged fields and ordinary photons under electric–magnetic dualization. The focus of this paper is the production of MMs through Drell–Yan (DY) and the Photon-Fusion (PF) mechanisms to generate velocity-dependent scalar, fermionic, and vector monopoles of spin angular momentum 0 , 1 2 , 1 respectively at LHC. A computational study compares the monopole pair-production cross-sections for both methods at various center-of-mass energies ( s ) with different magnetic dipole moments. The comparison of kinematic distributions of monopoles at Parton and reconstructed level are demonstrated for both DY and PF mechanisms. Extracted results showcase how modern machine-learning techniques can be used to study the production of MMs at the future proton-proton particle colliders at 100 TeV. We demonstrate the observability of MMs against the most relevant Standard Model background using multivariate methods such as Boosted Decision Trees, Likelihood, and Multilayer Perceptron. This study compares the performance of these classifiers with traditional cut-based and counting approaches, proving the superiority of our methods.

Design and Experimental Demonstration of Wavelength‐Selective Metamirrors on Sapphire Substrates

The increasing demand for novel mirror coating designs for new generation of gravitational wave detectors is stimulating significant research interest in investigations of reflective properties of metasurfaces. Given this strong interest, this article details a systematic methodology for fabricating reflecting metasurfaces (metamirrors) designed to operate at target wavelengths of 1064 or 1550 nm. The proposed metasurfaces consist of silicon cylindrical nanoparticles placed on a sapphire substrate. First, the dimensional parameters of the structures are thoroughly selected through numerical simulations combined with material characterization. The configurations are subsequently analyzed analytically to reveal the mirror effect, which arises from the excitation of electric and magnetic dipole moments. Following this, the metasurfaces are fabricated and experimentally characterized, demonstrating reflectivity exceeding 95% around the design wavelengths, which is in good agreement with theoretical predictions. Overall, the work demonstrates the feasibility and detailed methodology for the fabrication of thin, lightweight metamirrors capable of achieving near‐perfect reflectivity at the specified target wavelengths.

Comprehensive Analysis of Optical Resonances and Sensing Performance in Metasurfaces of Silicon Nanogap Unit

Metasurfaces composed of silicon nanogap units have a variety of optical resonances, including bound states in the continuum (BIC). We show comprehensive numerical results on metasurfaces of Si-nanogap units, analyze the optical resonances, and clarify optically prominent resonances as well as symmetry-forbidding resonances that are the BIC, based on the numerical analyses of optical spectra and resonant electromagnetic field distributions. Introducing asymmetry in the unit cell, the BIC become optically allowed, being identified as magnetic dipole, electric quadrupole, and magnetic quadrupole resonances. Moreover, the optical resonances are examined in terms of refractive index sensing performance. A pair of the resonances associated with electric field localization at the nanogap was found to be sensitive to the refractive index in contact with the metasurfaces. Consequently, the gap mode resonances are shown to be suitable for a wide range of refractive index sensing over 1.0–2.0.

Ultrafast Excitonic Transitions in Enantiopure and Racemic Squaraine Thin Films

ABSTRACTWhile chirality is a prevalent character of numerous biological and synthetic organic molecules, its selective absorption of circularly polarized light, known as circular dichroism (CD), is typically small due to intrinsically weak coupling between magnetic and electric dipoles. However, thin films of aggregated, enantiopure prolinol‐derived squaraine molecules (ProSQ‐C16) exhibit an unusually large excitonic CD signal, although the underlying mechanism is not yet known. In this study, we employ steady‐state and ultrafast transient absorption spectroscopy to investigate the nature and dynamics of excitons in aggregates of enantiopure and racemic ProSQ‐C16 thin films. Highly resembling transient responses of enantiopure thin films under excitations at different photon energies strongly indicate that a single type of aggregate dominates the linear optical response, that is, a strong red‐shifted (J‐like) and weak blue‐shifted (H‐like) absorption band. On the other hand, the transient properties of the racemic thin film deviate from this pattern and remain largely ambiguous. The short lifetime of excited states and coherent oscillations present in the dynamics of the transient absorption signal indicate that the early time dynamics are governed by a transition towards a dark intermediate state, which might arise from intermolecular charge transfer with potential contributions from the coupling of excitons to the vibrations. This non‐radiative relaxation pathway explains the unusually weak fluorescence of the predominately J‐like behaving aggregate. Our findings conclusively show that the chiral aggregate structure has a strong impact on the optical and dynamic response of the excitons and underline the significance of non‐Frenkel exciton states for the optical properties of anilino squaraine dyes.

Hard-scattering approach to strongly hindered electric dipole transitions between heavy quarkonia

The conventional wisdom in dealing with electromagnetic transition between heavy quarkonia is the multipole expansion, when the emitted photon has a typical energy of order quarkonium binding energy. Nevertheless, in the case when the energy carried by the photon is of order typical heavy quark momentum, the multipole expansion doctrine is expected to break down. In this work, we apply the “hard-scattering” approach originally developed to tackle the strongly hindered magnetic dipole (M1) transition [Y. Jia , ] to the strongly hindered electric dipole (E1) transition between heavy quarkonia. We derive the factorization formula for the strongly hindered E1 transition rates at the lowest order in velocity and αs in the context of the nonrelativistic QCD, and conduct a detailed numerical comparison with the standard predictions for various bottomonia and charmonia E1 transition processes. Published by the American Physical Society 2024

Orbital motion control of an electrically charged spacecraft

In this paper, the orbital motion of an electrically charged spacecraft in the gravitational and magnetic fields of the Earth is investigated. The “direct magnetic dipole” is considered as a model of the geomagnetic field. The nonlinear non-autonomous system of differential equations of motion of the spacecraft center of mass in the Cartesian and spherical coordinate systems is derived. The analytical study of the influence of the Lorentz force on the orbital motion of a charged spacecraft is carried out. The approximate solution of the differential system is found. The results of numerical simulation of the spacecraft orbital motion based on the derived system of differential equations are presented. The analytical and numerical solutions are compared. The problem of stabilizing the spacecraft’s center of mass in the orbital plane is considered. Feedback control methods based on the use of jet engines are proposed. The technical justification of the proposed control methods is carried out. As a result, stabilization of an electrically charged spacecraft in a small neighborhood of the plane of the initial orbit is achieved. The motion of a spacecraft with a variable electric charge is considered. Methods of controlling orbital motion due to low thrust as a result of the Lorentz force effect are proposed.