Magnetic response of topological insulator layer with metamaterial substrate induced by an electric point source

We studied the space weather effects on the South Atlantic Anomaly (SAA) magnetic response using Tsyganenko models. For the physical parameters characterizing the SAA, the study considered the minimum magnetic field, the location (longitude and latitude) of the SAA center, and the area of the SAA. Regarding the space weather parameters, we considered the solar wind dynamic pressure, the interplanetary magnetic field components, B_{yIMF} and B_{zIMF}, the Dst index, and the geodipole tilting angle. To study the magnetic field response of the SAA, several different versions of the Tsyganenko models, namely, T96, T01, and TS05, were used to describe the external magnetic field contributions. The main internal magnetic field was calculated by the International Geomagnetic Reference Field (IGRF-12). The magnetic field study of the SAA was realized in long- and short-term (seasonal and diurnal) variations. We found that the Dst index and the geodipole tilting angle were the strongest influencing parameters on the SAA magnetic field response at all altitudes. Moreover, it was revealed that both magnetic poles might be a possible cause of the SAA magnetic field response, resulting from the space weather conditions. Furthermore, the magnetic field behavior of the SAA was affected by hourly variations, where the largest changes occurred at dayside.

Enhancing Casimir repulsion via topological insulator multilayers

The polarizatison conversion and the Goos–Hänchen (GH) shifts of the reflected electromagnetic wave for the multilayered structure made of topological insulator (TI) layers with finite surface energy gap are investigated. The transfer matrix formalism is adopted to analyze the reflection of electromagnetic wave through the multilayered structure, and the influences of surface energy gap, thickness and number of the TI layers are discussed. We find that maximum polarization conversion rate can be obtained with appropriate surface energy gap of TI, and within a certain range of finite energy gap, the polarization conversion effect is stronger than that for the case under the infinite surface energy gap limit. Greater polarization conversion rate for TI with small surface energy gap can be found than that for TI with larger energy gap in some range of layer numbers. At large incident angles the GH shifts vary considerably with the layer number for TI with relatively larger energy gap. Result of the combined influence of surface energy gap and layer number shows that, there exists both the positive and negative enhancement peaks of the GH shifts, and for smaller energy gap, fewer TI layers are required to obtain the transition between positive and negative GH shifts.

Interlayer exchange coupling (IEC) between two magnetic layers sandwiched by a nonmagnetic spacer layer plays a critical role in shaping the magnetic properties of such heterostructures. The quantum anomalous Hall (QAH) effect has been realized in a structure composed of two magnetically doped topological insulator (TI) layers separated by an undoped TI layer. In this work, we employ molecular beam epitaxy to synthesize a series of magnetic TI sandwiches with varying thicknesses of the middle undoped TI spacer layer. The well-quantized QAH effect is observed in all these samples, and the IEC modulates its critical behavior between the top and bottom magnetic TI layers. Near the plateau phase transition (PPT), thinner QAH samples exhibit a two-dimensional critical metal behavior with nearly temperature-independent longitudinal resistance. In contrast, thicker QAH samples behave as a three-dimensional insulator with reduced longitudinal resistance at higher temperatures. We employ a magnetic TI Hamiltonian with random magnetic domains to understand the IEC-induced critical-metal-to-insulator transition observed near QAH PPT.

The rapid change in the Earth’s magnetosphere caused by solar wind disturbances has been an important part of the solar wind-magnetosphere interaction. However most of the previous studies focused on the perturbation of the Earth’s magnetic field caused by solar wind dynamic pressure changes. In this paper, we studied the response of geosynchronous magnetic field and the magnetic field to the rapid southward turning of interplanetary magnetic field during the interval 1350–1420 UT on 7 May 2007. During this event, BZ component of the interplanetary magnetic field decreased from 15 nT to −10 nT within 3 min (1403–1406 UT). The geosynchronous magnetic field measured by three geosynchronous satellites (GOES 10–12) first increased and then decreased. The variations of magnetic field strength in the morning sector (9–10 LT) were much larger than those in the dawn sector (5 LT). Meanwhile, the H components of geomagnetic field on the ground have similar response features but exhibit latitude and LT dependent variations. Compared with H components, the D components do not have regular variations. Although the solar wind dynamical pressure encounters small variations, the magnetic field both in space and on the ground does not display similar variations. Therefore, the increase of geomagnetic field in the dawn sector is caused by the southward turning of IMF (interplanetary magnetic field) BZ. These results will help to better understand the coupling process of geomagnetic filed and interplanetary magnetic field.

Advances in Biomagnetic Liver Susceptometry Allow the Measurement of Liver Iron Concentration with a Room Temperature Sensor

Electric and magnetic field responses originating from a primary electric current source have been analytically derived, explored, and employed to explore and detect electrical anomalies due to the presence of a bed boundary in a two-layer model, using the controlled source electromagnetic method. However, previous works on the subject demand in-depth knowledge of mathematics, which could become an obstacle for the practitioner looking to immerse into the realm of induction logging and who needs a straightforward approach to develop their algorithms. Consequently, we introduce the analytical expressions for electric and magnetic field responses to an electric current dipole source arbitrarily oriented in one-dimension (1D) transversely isotropic media. In addition, we apply these equations to examine both electric and magnetic field responses to a distant resistive anomaly from electric transverse electric dipole transmitters. Our analysis shows that magnetic field responses are significantly more sensitive to the anomaly ahead of the tool for a vertical or a horizontal borehole. While the coplanar electric field measurements with conventional electric resistivity tools are known to be sensitive to the resistivity anomaly around the tool, the axial magnetic field measurement using the transverse electric dipole transmitter and the transverse magnetic field measurement using an axial electric dipole transmitter are significantly more sensitive to the anomaly around the tool than any electric field measurements. This deep-looking capability is achieved with a relatively short source-receiver spacing of 10 m. Based on the increased deep-looking capability, we encourage the use of magnetic components from our generalized geosteering tool based on electric dipole sources because it can potentially flag anomalies at a distance 60% further in comparison to the sensitivity of electric measurements.

Hydrocarbon reservoirs can be mapped if sufficient resistivity contrasts exist between them and their confining layers, but practical problems remain in target discrimination in deep and shallow waters, especially in the presence of heterogeneous overburden. We have developed an efficient 3D staggered-grid finite-difference controlled-source electromagnetic (CSEM) modeling code that enables study of the physics underlying some practical problems. We undertook a comparative analysis of reservoir detection in [Formula: see text]- and [Formula: see text]-deep waters using the simulated electric and magnetic field responses of a simple 3D reservoir. We examined the effect of two types of near-surface heterogeneity (mimicking disconnected gas clouds and/or patchy geochemical alteration halos) on the 3D reservoir response. We found that small-scale, shallow heterogeneities cause distortions that are almost independent of the source frequency. These persist at all source-receiver offsets in the electric amplitude response in deep and shallow waters and phase response in shallow water. They decrease in magnitude with increasing offset in deepwater phase response. Large-scale near-surface heterogeneities distort the horizontal electric field response more significantly than the small-scale ones, but the near-surface response gets smaller in amplitude as the offset increases. The distortions in shallow water are much smaller in magnitude than those for the deepwater case, so that the reservoir signatures still are visible on the response profiles. This might be considered as a positive feature for shallow-water inline electric field exploration. The magnetic field responses for the orthogonal direction provide diagnostic target signatures that are similar to the inline electric field responses in deep water but that are different in shallow water. The magnetic responses are affected by the airwave in a different manner from the electric field, suggesting that combined 3D electric and magnetic field analysis might be vital for handling the airwave problem.

Topological insulators are a new class of materials characterized by fully spin-polarized surface states, a linear dispersion, imperviousness to external non-magnetic perturbations, and a helical character arising out of the perpendicular spin-momentum locking. This article answers in a pedagogical way the distinction between a topological and normal insulator, the role of topology in band theory of solids, and the origin of these surface states. Numerical techniques including diagonalization of the TI Hamiltonians are described to quantitatively evaluate the behaviour of topological insulator states. The Hamiltonians based on continuum and tight binding approaches are contrasted. The application of TIs as components of a fast switching environment or channel material for transistors is examined through I-V curves. The potential pitfall of such devices is presented along with techniques that could potentially circumvent the problem. Additionally, it is demonstrated that a strong internal electric field can also induce topological insulator behaviour with wurtzite nitride quantum wells as representative materials.

Ageing in Li-ion batteries is a prime concern, due to the rapid increase of their use as a power source for numerous applications from stationary applications to automotive industries. During a battery lifetime, state of health is deteriorating due to irreversible physical and chemical changes like loss of active Li+ ions, internal resistance rise, solid electrolyte interphase (SEI) growth, electrolyte oxidation and loss of active electrode material. This paper aims to demonstrate the potential of a non-invasive method: Magnetic Field Probing (MFP) for monitoring loss of porosity due to ageing in the battery. A multi-physics model using COMSOL Multiphysics simulation tool evaluates the magnetic field response, battery polarization (ohmic potential drop) and internal resistance (IR) of the Li-ion battery. The electrode porosity variation has a significant influence on the magnetic field response (MFR). The analysis shows that the porosity loss at graphite electrode has a major impact on the battery ageing factors (polarization and internal resistance). Moreover, research work infers that the MFR and IR have higher sensitivity at the anode. Approach: The Li-ion battery works on rock n chair concept. Li-ions travels back and forth between electrodes. The concentration of Li-ion shows the amount of energy the battery contains. During simulation the external magnetic field is applied with Li-ion battery module.Li-ion is a paramagnetic ion that alters the magnetic field. At anode, the change in Li-ions concentration during cycling will certainly change the applied magnetic field.Lithium metal oxide is used as cathode material. During charge-discharge cycle, lithium metal oxide converts to metal oxide. The process changes the phase and valency of metal ions. The phase and valency change of ions affect its magnetic properties and alters the value of applied magnetic field.The model uses LiMn2O4 as the cathode, LiC6 as the anode, and the electrolyte consists of LiPF6 salt in 1:2 EC:DMC solvent. A bidirectional coupling is used between the Li-ion battery an external applied magnetic field. Physics based Li-ion battery model equations and standard Maxwell's and Lorentz force equations are coupled Figure 1

A magnetic field response recorder was developed to facilitate a measurement acquisition method that uses magnetic fields to power and to interrogate all sensors. Sensors are designed as electrically passive inductive-capacitive or passive inductive-capacitive-resistive circuits that produce magnetic field responses when electrically activated by oscillating magnetic fields. When electrically activated, the sensor's magnetic field response attributes (frequency, amplitude and bandwidth) correspond to the one or more physical states that each sensor measures. The response recorder makes it possible to simultaneously measure two unrelated physical properties using this class of sensors. The recorder is programmable allowing it to analyze one or more response attributes simultaneously. A single sensor design will be used to demonstrate that the acquisition method and the sensor example can be used to for all phases of a component's life from manufacturing to damage that can destroy it.

The degaussing process is crucial for ensuring magnetic protection in ships. It involves the application of oscillating and attenuating magnetic fields to eliminate residual magnetism in the ship’s structure. However, this process can lead to the generation of distorted magnetic fields within the ship’s cabin, posing a potential threat to electronic equipment performance. Therefore, it is essential to have a comprehensive understanding of the dynamic magnetic field response in ship structures to develop effective degaussing systems. To address this need, this paper proposes an eddy current model for analyzing the dynamic magnetic field response in ferromagnetic metal structures. This model focuses on the role of eddy currents in shaping the magnetic field response and provides valuable insights into the underlying mechanisms. Using the proposed eddy current model, the effects of key system parameters such as thickness, conductivity, and the length-scale of the ship structure can be analytically investigated. This analysis helps in understanding how these parameters influence the dynamic magnetic field response and aids in the design and optimization of degaussing systems. The effectiveness and applicability of the proposed eddy current model are demonstrated through comprehensive investigations involving two simulation cases of varying complexity. The model accurately predicts the changing trends of the dynamic magnetic field response, as confirmed through finite element simulations. This validation highlights the model’s ability to reproduce simulation results accurately and its potential as a powerful tool for analyzing and optimizing dynamic magnetic field responses. In summary, the proposed eddy current model represents a significant advancement in the field. It provides a valuable theoretical framework for understanding and analyzing the dynamic magnetic field response in ferromagnetic metal structures. By offering insights into the underlying mechanisms and the influence of key parameters, this research contributes to the development of improved degaussing systems and enhances the overall magnetic protection capabilities of ships.

This paper presents a non-contact method for powering and interrogating magnetic field response sensors that facilitates measurement of multiple unrelated physical quantities using the same sensor. The sensors are electrically passive inductive–capacitive or passive inductive–capacitive–resistive circuits that are powered using oscillating magnetic fields, and once electrically active, the sensors respond with their own oscillating magnetic fields. The sensor's magnetic field response frequency, amplitude and bandwidth are correlated to the magnitude of one or more physical quantities that each sensor measures. The magnetic field response sensors and the technique for powering and interrogation alleviate many shortcomings of traditional sensor/measurement systems. The shortcomings are having a data acquisition channel dedicated to each sensor, wiring/circuitry weight associated with measurements, electrical arcing, wire degradations due to wear or chemical decay and the logistics needed to add new sensors. Because measurements can be derived from influences upon the sensor's magnetic field or electrical field, the circuit that forms the sensor need not be in physical contact with the measurand. The method for discerning sensor response frequency, resistance and amplitude is presented herein. The method does not require the sensors to be near or physically connected to acquisition hardware or a power source. The theoretical basis for the measurement acquisition technique is discussed including the influence of key parameters on measurement acquisition. One example of a magnetic field response sensor for measuring the magnitude of three unrelated physical quantities—material phase transition, temperature and position—will be presented. A fluid-level measurement will also be presented.

SUMMARYWe developed a compact susceptometer employing a high‐temperature superconductor (HTS) superconducting quantum interference device (SQUID) that can measure the M–H characteristics and the harmonic components induced in the ac magnetic field response from a sample. In the dc function for measuring M–H characteristics, the sample was vibrated in a dc magnetic field, and the secondary magnetic field generated from the sample was detected by a dc pickup coil. In the ac function for measuring harmonic components, the sample placed in an ac magnetic field, and the ac response was detected by an ac pickup coil. The pickup coil is connected in series with the input coil, which is inductively connected to the HTS‐SQUID. A signal from the HTS‐SQUID was transmitted to a lock‐in amplifier and was analyzed as the intensity and phase of the measured magnetic field. In order to clarify the basic properties of the system, we measured the ac magnetic field response from a sample while varying the relative positions of the sample and the pickup coil, and the M–H characteristics while varying the dc bias magnetic field intensity. Furthermore, by analyzing the harmonic components of the ac/dc magnetic field response, the proposed system can measure magnetic field properties with high sensitivity and at high speed.

With the increasing complexity of flexible sensor application scenarios, in order to achieve their use in electric and magnetic fields, this paper introduces a core‐shell structure with Ni‐doped cobalt ferrites as the magnetic core and barium titanate as the dielectric layer, filling it into a polymer matrix to prepare flexible magneto‐dielectric elastomer composites. Taking advantages of this design, the targets including the establishment of multi‐functionalization and the retention of fine mechanical properties have been simultaneously achieved. The synthesized elastomer composites exhibit fine flexibility and excellent magneto‐electric response. An optimum magnetic‐induced deformation angle achieves to 55° under an external magnetic field of 8000 Oe, and a maximum electric‐induced deformation approaches to about 8.29% under an applied electric field of 5 kV/mm. Besides that, with Ni‐doping, the magnetization behaviors of composite fillings could be tuned, resulting a controllable magnetic field response of the synthesized magneto‐dielectric rubber composites. This work provides a novel way to design multi‐functionalized flexible composites, which is significant for exploring multi‐mode flexible sensors.Highlights Magneto‐dielectric elastomers were prepared with using core‐shell filling. The elastomer composites exhibit fine magnetic and electric field response. The composites maintained good flexible mechanical properties.