Nonmagnetic Conductors Research Articles

Fiber-based Probes for Electrophysiology, Photometry, Optical and Electrical Stimulation, Drug Delivery, and Fast-Scan Cyclic Voltammetry In Vivo.

Recording and modulation of neuronal activity enables the study of brain function in health and disease. While translational neuroscience relies on electrical recording and modulation techniques, mechanistic studies in rodent models leverage genetic precision of optical methods, such as optogenetics and imaging of fluorescent indicators. In addition to electrical signal transduction, neurons produce and receive diverse chemical signals which motivate tools to probe and modulate neurochemistry. Although the past decade has delivered a wealth of technologies for electrophysiology, optogenetics, chemical sensing, and optical recording, combining these modalities within a single platform remains challenging. This work leverages materials selection and convergence fiber drawing to permit neural recording, electrical stimulation, optogenetics, fiber photometry, drug and gene delivery, and voltammetric recording of neurotransmitters within individual fibers. Composed of polymers and non-magnetic carbon-based conductors, these fibers are compatible with magnetic resonance imaging, enabling concurrent stimulation and whole-brain monitoring. Their utility is demonstrated in studies of the mesolimbic reward pathway by simultaneously interfacing with the ventral tegmental area and nucleus accumbens in mice and characterizing the neurophysiological effects of a stimulant drug. This study highlights the potential of these fibers to probe electrical, optical, and chemical signaling across multiple brain regions in both mechanistic and translational studies.

The use of a swept frequency alternating current potential difference method for identifying local geometric features within prismatic conductors

Potential difference methods are widely accepted as means to detect and monitor cracks in safety critical components. This paper investigates the capability of the potential difference method that uses a swept frequency alternating current excitation (i.e. skin effect with varying current penetration depths) in identifying conductor shapes and features through experiments and finite element analysis. The study focused on samples with the size of 55 mm × 100 mm2 and surface features with opening widths vary from 11% to 42% to the sample size. The method has been investigated by finite element analysis with the capability to distinguish cross-sectional shapes of non-magnetic conductors due to prominent current crowding on surfaces, in which the potential differences measured from a SS316 conductor of triangular cross-sectional shape are higher to those of a circular shape by 77% at 300 kHz. The detection capability of the method has also be confirmed, which is attributed to the impact of feature openings on skin effect. At 50 kHz, potential differences measured across features with the same cross-sectional area of 9 mm2 on EN1A samples rise by 130% as the opening width increase from 11% to 42% to the sample size.

Observation of the Anisotropic Magneto-Thomson Effect.

We report the observation of the anisotropic magneto-Thomson effect (AMTE), which is one of the higher-order thermoelectric effects in a ferromagnet. Using lock-in thermography, we demonstrated that in a ferromagnetic NiPt alloy, the cooling or heating induced by the Thomson effect depends on the angle between the magnetization direction and the temperature gradient or charge current applied to the alloy. AMTE observed here is the missing ferromagnetic analog of the magneto-Thomson effect in a nonmagnetic conductor, providing the basis for nonlinear spin caloritronics and thermoelectrics.

Orbital Hanle Magnetoresistance in a 3d Transition Metal.

The Hanle magnetoresistance is a telltale signature of spin precession in nonmagnetic conductors, in which strong spin-orbit coupling generates edge spin accumulation via the spin Hall effect. Here, we report the existence of a large Hanle magnetoresistance in single layers of Mn with weak spin-orbit coupling, which we attribute to the orbital Hall effect. The simultaneous observation of a sizable Hanle magnetoresistance and vanishing small spin Hall magnetoresistance in BiYIG/Mn bilayers corroborates the orbital origin of both effects. We estimate an orbital Hall angle of 0.016, an orbital relaxation time of 2ps and diffusion length of the order of 2nm in disordered Mn. Our findings indicate that current-induced orbital moments are responsible for magnetoresistance effects comparable to or even larger than those determined by spin moments, and provide a tool to investigate nonequilibrium orbital transport phenomena.

Electrophysical Mechanism of Appearance of the Phenomenon of Superficial Effect in a Metallic Conductor with the Alternating Electric Current

An electrophysical mechanism explaining the origin of an uneven distribution of the field strength of the intrinsic alternating electromagnetic field (EMF) over the thickness of the bulk homogeneous nonmagnetic metal conductor with a rectangular cross-section with an alternating current i0(t) of different peak-temporal parameters is suggested. This mechanism, justifying the manifestation of the surface effect in the specified conductor, is based on the Faraday–Maxwell law of electromagnetic induction. It is mathematically shown that inductive alternating conduction currents and their alternating EMF arising in the conductor material due to the action of an alternating conduction current i0(t) and, accordingly, an intrinsic alternating magnetic flux Ф0(t) at dФ0(t)/dt>0 weaken the intrinsic alternating EMF strength distributed inside the conductor, and at dФ0(t)/dt<0 they maintain the EMF strength diminishing with time and the material depth.

Analysis and Application of a Surface Admittance Operator for Combined Magnetic and Dielectric Contrast in Emerging Interconnect Topologies

In state-of-the-art interconnect design, topologies including magnetic materials, such as the so-called superlattice conductors, are rapidly emerging as a novel strategy to handle the challenges associated with the evolution toward higher operating frequencies and integration densities. Consequently, it is imperative that the newly developed full-wave electromagnetic solvers rigorously model these innovative materials and still accurately capture phenomena such as the skin and proximity effect in good conductors. In this article, we propose such a method to rigorously characterize this important class of interconnects with arbitrary, possibly frequency-dependent, material properties, including combined dielectric and magnetic contrast. To that end, a 2-D differential surface admittance (DSA) operator is used, which invokes a single-source equivalence theorem to model both nonmagnetic and magnetic conductors efficiently. This operator is combined with the electric field integral equation (EFIE), yielding a comprehensive formalism to extract the pertinent per-unit-of-length (p.u.l.) resistance and inductance parameters of the modeled structures. The numerical properties of our technique are studied in detail, with particular attention to the influence of magnetic materials. Finally, various relevant application examples are considered to establish its correctness and versatility.

Spin-charge-coupled transverse resistance in an ambipolar conductor YH2-based Hall-bar structure with perpendicularly magnetized current-injection electrodes

Spin-charge (SC) coupling is crucial in spintronics and the coupling mechanisms can be classified into bulk characteristic via spin-orbit interaction (SOI) or the interfacial characteristic provided by a junction formed by magnetic and nonmagnetic conductors. The two types of SC couplings account for the transverse resistance (TR) in a planer channel subjected to out-of-plane-polarized spin current injection. This is because interfacial spin-accumulation induces the diffusive transport of spin-angular momentum, which is converted into transverse charge accumulation via SOI. We explore the SC coupling characteristics of a lateral junction consisting of (i) a rare-earth transition metal (RE-TM) ferrimagnet with perpendicular magnetic anisotropy and (ii) a compensated metal, YH2, where electrons and holes simultaneously participate in spin and charge transports. This set-up allows us to observe the TR, which mirrors the magnetization of the RE-TM employed as the current-source electrode in the planer Hall-bar structure. The results show that the inverse spin Hall effect contributes significantly to the TR. Along with the TR measurement, we formulate a minimal expression of the TR when out-of-plane-polarized electron and hole spin currents are injected from the magnetic electrode. Since this formulation is independent of the details of the SC coupling mechanism, it is applied to interpret the observation result to reveal the SC coupling characteristics of the RE-TM and YH2 set-up.

Quantitative evaluation of corrosion in conductors under stress via GPEC

Macroscopic defects such as corrosion in nonmagnetic Conductors Under Stress (CUS) are more universal than those within the zero-stress environment, and result in complicated characteristics regarding the electrical properties of the conductors. In this paper, Gradient-field Pulsed Eddy Current technique (GPEC) is intensively investigated for imaging and evaluation of corrosion in CUS. The influence of stress on electrical properties of nonmagnetic CUS with corrosion is analysed via multi-physics simulations and experiments. The correlations between characteristics of corrosion in CUS and the GPEC signal and its features are established and scrutinised. An image processing method reproducing defect images for quantitative assessment of detected corrosion in CUS is proposed.

Direct X-Ray Detection of the Spin Hall Effect in CuBi

The spin Hall effect and its inverse are important spin-charge conversion mechanisms. The direct spin Hall effect induces a surface spin accumulation from a transverse charge current due to spin orbit coupling even in non-magnetic conductors. However, most detection schemes involve additional interfaces, leading to large scattering in reported data. Here we perform interface free x-ray spectroscopy measurements at the Cu L_{3,2} absorption edges of highly Bi-doped Cu (Cu_{95}Bi_{5}). The detected X-ray magnetic circular dichroism (XMCD) signal corresponds to an induced magnetic moment of (2.7 +/- 0.5) x 10-12 {\mu}_{B} A^{-1} cm^{2} per Cu atom averaged over the probing depth, which is of the same order as for Pt measured by magneto-optics. The results highlight the importance of interface free measurements to assess material parameters and the potential of CuBi for spin-charge conversion applications.

A space-time discretization for an electromagnetic problem with moving non-magnetic conductor

This paper deals with a space-time discretization scheme for an eddy current problem in a multi-component domain with a moving non-magnetic conductor. We incorporate the Coulomb gauge to the formulation, then propose a fully-discrete finite element scheme combined with backward Euler's method to find an approximation of the solution to the variational system. The convergence of the scheme is proved, and the error estimates for the first-order Lagrangian finite elements are established. Under appropriate assumptions on the weak solution and the given initial data, we show the optimal convergence rate for the space discretization and the suboptimal rate for time discretization. Some numerical experiments are performed to support the obtained theoretical results.

Особенности распространения стоячих электромагнитных и электронных волн в металлическом проводнике с электрическим переменным током проводимости

The paper demonstrates the results of approximate calculations on the establishment of basic features of the propagation of standing transversal electromagnetic waves (EMWs) and standing longitudinal de Broglie electronic waves in a homogeneous not massive non-magnetic metallic conductor of finite dimensions (the radius r0 and the length l0 >>r0) with the alternating axial-flow current of conductivity of i0(t) of different peak-temporal parameters. The correlation for the rated estimation of the average velocity of propagation of the standing transversal EMWs and standing longitudinal de Broglie electronic waves in a metal (alloy) of the indicated conductor is presented. It is shown that quantized standing transversal EMWs arising in a metallic conductor of finite dimensions substantially differ from ordinary transversal EMWs, propagated in the conducting environments of unlimited dimensions. An important feature of the standing transversal EMWs in the examined conductor is the fact that their tension of an axial-flow electric-field advances by a phase their tension of an azimuthal magnetic-field on the corner of π/2. It was established that in the standing transversal EMWs of the used conductor the energy of their electric field only passes into the energy of their magnetic field and vice versa. Therefore the standing transversal EMWs do not transfer the flows of the electromagnetic energy on the surface of the studied conductor.

DFT Electronic Properties and Synthesis Thermodynamics of Li x La1−x TiO3 Electrolytes for Li-Ion Batteries

Lithium lanthanum titanate perovskites Li x La1−x TiO3 (LLTO) are promising solid-electrolytes for Li-ion batteries. We studied, in the Density-Functional-Theory framework, the thermodynamic stability and the electronic and magnetic properties of LLTO, as bulk materials and as thin slabs with (001) exposed surfaces. Results show that LaTiO3 (LTO) exhibits semiconductor behavior and G-type antiferromagnetic order (AFMG), whereas the TiO2-terminated LTO slab is a semiconductor with ferromagnetic (FM) order. Contrasting, the LTO slab exposing a LaO-terminated surface is a conductor with AFMG ordered Ti cations' magnetic moments (MMs), but at the surface there are some FM ordered MMs (La atoms). LLTO bulk electrolyte is a semiconductor (x = 0.25) or insulator (x = 0.50). The LLTO slab is a FM (non-magnetic) conductor (TiO2 (LiO)-terminated surface) or a FM semiconductor (LaO-terminated). Besides, the stability of the LLTO bulk and slabs structures was analyzed, as well as the slabs’ preferences for LiO, LaO or TiO2 ends.

Generating a Topological Anomalous Hall Effect in a Nonmagnetic Conductor: An In-Plane Magnetic Field as a Direct Probe of the Berry Curvature

We demonstrate that the Berry curvature monopole of nonmagnetic two-dimensional spin-3/2 holes leads to a novel Hall effect linear in an applied in-plane magnetic field B_{∥}. Remarkably, all scalar and spin-dependent disorder contributions vanish to leading order in B_{∥}, while there is no Lorentz force and hence no ordinary Hall effect. This purely intrinsic phenomenon, which we term the anomalous planar Hall effect (APHE), provides a direct transport probe of the Berry curvature accessible in all p-type semiconductors. We discuss experimental setups for its measurement.

Error estimates for the time discretization of an electromagnetic contact problem with moving non-magnetic conductor

In the present paper, we investigate an eddy current problem in a three-dimensional domain containing a moving non-magnetic workpiece. A time discretization scheme based on the backward Euler method is proposed to approximate the original problem. The convergence of the scheme is proved using the Reynolds transport theorem and the corresponding error estimates are derived under appropriate assumptions. Some numerical results are also presented to assess the performance of the proposed scheme as well as to confirm the obtained error estimates.

Research on the Non-Magnetic Conductor of a PMSM Based on the Principle of Variable Exciting Magnetic Reluctance

A permanent magnet synchronous motor (PMSM) based on the principle of variable exciting magnetic reluctance (VMRPMSM) is presented. The motor is equipped with symmetrical non-magnetic conductors on both sides of the tangential magnetized permanent magnets (PMs). By placing the non-magnetic conductor (NMC), the magnetic reluctance in the exciting circuit is adjusted, and the flux weakening (FW) of the motor is realized. Hence, the NMC is studied comprehensively. On the basis of introducing the motor structure, the FW principle of this PMSM is described. The shape of the NMC is determined by analyzing and calculating the electromagnetic force (EF) acting on the PMs. We calculate the magnetic reluctance of the NMC and research on the effects of the NMC on electromagnetic force, d-axis and q-axis inductance and FW performance. The critical speeds from the test of the no-load back electromotive force (EMF) verify the correctness of the NMC design. The analysis is corresponding to the test result which lays the foundation of design for this kind of new PMSM.

A magnetic damper for low temperature

A new magnetic damper is developed for the suspension and vibration isolation of precise instruments working in low-temperature and vacuum environments. The damper comprises permanent magnets, a non-magnetic conductor tube, and a spring, and a room-temperature prototype is designed in COMSOL Multiphysics and verified by experiments. A tubular eddy current damper is chosen because it has less leakage flux than the flat type and better usage of magnetic flux, which leads to higher eddy currents. The adjacent magnets arranged in the reverse direction of magnetization can contribute to obtaining a compact damper. COMSOL Multiphysics is proven to be effective software to predict the performance of an eddy current damper compared with the existing experimental and theoretical results. To apply the damper to low-temperature conditions, the selections of non-magnetic tubes and the permanent magnet are thoroughly analyzed. This study offers the applicability of the magnetic damper in the suspension and vibration isolation of precise instruments and provides suggestions for the design of low-temperature and vacuum magnetic dampers.

The Performance of the Magneto-Impedance Effect for the Detection of Superparamagnetic Particles.

The performance of magneto-impedance sensors to detect the presence and concentration of magnetic nanoparticles is investigated, using finite element calculations to directly solve Maxwell’s equations. In the case of superparamagnetic particles that are not sufficiently magnetized by an external field, it is assumed that the sensitivity of the magneto-impedance sensor to the presence of magnetic nanoparticles comes from the influence of their magnetic permeability on the sensor impedance, and not from the stray magnetic field that the particles produce. The results obtained not only justify this hypothesis, but also provide an explanation for the discrepancies found in the literature about the response of magneto-impedance sensors to the presence of magnetic nanoparticles, where some authors report an increasing magneto-impedance signal when the concentration of magnetic nanoparticles is increased, while others report a decreasing tendency. Additionally, it is demonstrated that sensors with lower magneto-impedance response display larger sensitivities to the presence of magnetic nanoparticles, indicating that the use of plain, nonmagnetic conductors as sensing materials can be beneficial, at least in the case of superparamagnetic particles insufficiently magnetized in an external magnetic field.

Analysis of field uniformity and quantitative evaluation of subsurface pitting corrosion in conductors via GPEC

Structures of nonmagnetic materials are broadly used in engineering fields such as aerospace, energy, etc. Due to corrosive and hostile environments, they are vulnerable to the Subsurface Pitting Corrosion (SPC) leading to structural failure. Therefore, it is imperative to conduct periodical inspection and comprehensive evaluation of SPC using reliable nondestructive evaluation techniques. Extended from the conventional Pulsed eddy current method (PEC), Gradient-field Pulsed Eddy Current technique (GPEC) has been proposed and found to be advantageous over PEC in terms of enhanced inspection sensitivity and accuracy in evaluation and imaging of subsurface defects in nonmagnetic conductors. In this paper two GPEC probes for uniform field excitation are intensively analyzed and compared. Their capabilities in SPC evaluation and imaging are explored through simulations and experiments. The optimal position for deployment of the magnetic field sensor is determined by scrutinizing the field uniformity and inspection sensitivity to SPC based on finite element simulations. After the optimal probe structure is chosen, quantitative evaluation and imaging of SPC are investigated. Signal/image processing algorithms for SPC evaluation are proposed. Through simulations and experiments, it has been found that the T-shaped probe together with the proposed processing algorithms is advantageous and preferable for profile recognition and depth evaluation of SPC.

PECULIARITIES OF THE MANIFESTATION AND INFLUENCE ON THE ELECTROMAGNETIC PROCESSES OF THE TRANSIENT SKIN EFFECT IN METAL CONDUCTORS WITH PULSED CURRENT

Purpose. Preparation of brief scientific review of basic results of the known theoretical researches of the electrophysics phenomenon of linear transient skin effect (TSE) in the non-magnetic homogeneous massive conductors of flat and cylindrical configurations on which in the discharge electric circuits of high-voltage electrophysical installations (EPHI) the pulsed currents ip(t) flow with given amplitude-temporal parameters (ATPs). Methodology. Theoretical bases of electrical engineering, bases of theoretical electrophysics, electrophysics bases of technique of high-voltage and high pulsed currents. Results. The brief scientific review of results of the known theoretical researches of the electrophysical phenomenon of linear TSE in non-magnetic homogeneous massive flat and cylindrical metal conductors with pulsed axial (azimuthal) current ip(t), formed in the discharge circuit of powerful high-voltage EPHI. In the generalized and systematized form the basic features of manifestation of linear TSE in the indicated conductors and influence of the considered skin effect on electromagnetic processes are presented at flow in conductors and discharge circuit of a high-voltage EPHI with the pulsed current ip(t) time-varying by law of attenuated sinewave. Influence of linear TSE is described in non-magnetic massive conductors during transient in a discharge circuit of EPHI with the pulsed current ip(t) of given ATP, depth of penetration of the electromagnetic field in materials of the indicated conductors, own integral electric parameters of the considered conductors and their good quality in the high-current discharge circuit of high-voltage EPHI. It is shown that at the analysis of electromagnetic transients in high-current discharge electric circuits of powerful high-voltage EPHI it is necessary to take into account flowing in materials of the examined massive conductors of such known electrophysical phenomenon as linear TSE. Originality. Generalization and systematization is first executed regarding domestic and foreign scientists-electrical engineers’ results of theoretical researches for long-term period of the electrophysics phenomenon of linear TSE in the flat and cylindrical metallic conductors of different thickness with the pulsed current ip(t)of given ATP. Practical value. The results presented in the generalized and systematized form will be useful for electrical engineers in deepening of understanding of basic features of manifestation in non-magnetic massive homogeneous conductors with the pulsed current ip(t) of given ATP of such widely widespread in area of high-voltage high-current pulsed technique electrophysics phenomenon as linear TSE and its influences on electromagnetic transients in similar metallic conductors and high-current discharge circuits of high-voltage EPHI.

Electronic and magnetic properties of B-Doped XS (X = Zn and Cd): A density functional theory study

Ab-initio calculations were performed to study the electronic and magnetic properties of boron doped XS (X = Zn and Cd) systems. The structural stability of doped systems is analyzed in terms of formation energy and found that B@S site in ZnS is more energetically favorable than that of B@S in CdS system. Our calculations show that B-doping at S-site (B@S) induced magnetism in XS structures, which can be explained on the basis of electronegativity difference between the dopant and host atoms. It is evident that B 2p orbitals are playing the major role to generate magnetism in both (ZnS and CdS) doped systems. In contrast, B-doping at Zn/Cd sites in XS structures, leads the systems to n-type non-magnetic conductor. Furthermore, the impact of B-doping at different S sites is studied to probe the stable magnetic ground state. Finally, the magnetic transition temperature (Tc) is also computed.