Electromagnetic Proximity Research Articles

Absence of magnetic interactions in Ni–Nb ferromagnet–superconductor bilayers

Studies of ferromagnet-superconductor hybrid systems have uncovered magnetic interactions between the competing electronic orderings. The electromagnetic (EM) proximity effect predicts the formation of a spontaneous vector potential inside a superconductor placed in proximity to a ferromagnet. In this work, we use a Nb superconducting layer and Ni ferromagnetic layer to test for such magnetic interactions. We use the complementary, but independent, techniques of polarized neutron reflectometry and detection Josephson junctions to probe the magnetic response inside the superconducting layer at close to zero applied field. In this condition, Meissner screening is negligible, so our measurements examine only additional magnetic and screening contributions from proximity effects. We report the absence of any signals originating from EM proximity effect in zero applied field. Our observations indicate that either EM proximity effect is below the detection resolution of both of our experiments or may indicate a new phenomenon that requires extension of current theory. From our measurements, we estimate a limit of the size of the zero field EM proximity effect in our Ni–Nb samples to be ±0.27 mT.

Electromagnetic proximity effect in superconductor/ferromagnet bilayers with in-plane magnetic texture

The so-called electromagnetic proximity effect manifests itself as the long-range leakage of the magnetic field from a ferromagnet (F) to a superconductor (S), which is in electrical contact with the ferromagnet. In the present paper, we study the proximity-induced supercurrent and magnetic field in S/F bilayer systems with an in-plane inhomogeneous ferromagnet. We find that at the S/F interface a spontaneous surface current appears which is perpendicular to the local in-plane magnetization. In this sense, S/F bilayers with a metallic ferromagnet mimic similar systems with an insulating ferromagnet, where a surface current appears due to the interplay of the exchange field and Rashba spin-orbit coupling. We consider three geometrical configurations of the ferromagnet: a uniformly magnetized strip, an infinite slab with two domains and a Néel wall between them, and a ferromagnetic disk with a magnetization vortex. It is found that the proximity effect in the magnetic strip geometry induces a magnetic field outside the ferromagnet (which vanishes in the absence of proximity coupling between S and F), and in the other two geometries it enhances the magnetic field far from the domain wall or the core of the magnetic vortex. Possible experimental methods to probe the described features are discussed.

Giant electromagnetic proximity effect in superconductor/ferromagnet superlattices

We show that in superlattices with alternating superconducting (S) and ferromagnetic (F) layers the spontaneous magnetic field induced in the superconducting layers due to the electromagnetic proximity effect becomes dramatically enhanced compared to the previously studied S/F bilayers. The effect reveals itself for the in-plane orientation of the magnetic moments both for ferromagnetic and anti-ferromagnetic ordering of the moments in the F layers. In the finite size samples the magnetic field decays from the sample surface towards the bulk of the structure, and the decay length strongly depends on the relative orientation of the sample surface, the layers planes and magnetic moments in the F layers. The obtained results provide additional insights into experimental data on the neutron scattering in Nb/Gd superlattices.

Meissner screening as a probe for inverse superconductor-ferromagnet proximity effects

We present experimental results on the observed flux screening in proximity coupled superconductor-ferromagnet thin film structures using Nb and Co as the superconductor and ferromagnet respectively. Using the low-energy muon-spin rotation technique to locally probe the magnetic flux density, we find that the addition of the ferromagnet (F) increases the total flux screening inside the superconductor. Two contributions can be distinguished. One is consistent with the predicted spin-polarization (or magnetic proximity) effect, while the other is in line with the recently emerged electromagnetic (EM) proximity models. Furthermore, we show that the addition of a few nanometers of a normal metallic layer between the Nb and the Co fully destroys the contribution due to electromagnetic proximity. This is unanticipated by the current theory models in which the magnetization in the F layer is assumed to be the only driving force for the EM effect and suggests the role of additional factors. Further experiments to explore the influence of the direction of the F magnetization also reveal deviations from theory. These findings are an important step forward in improving the theoretical description and understanding of proximity coupled systems.

Inverse magnetic hysteresis of the Josephson supercurrent: Study of the magnetic properties of thin niobium/permalloy (Fe20Ni80 ) interfaces

We propose a picture for the magnetic properties of superconductor/ferromagnet (S/F) heterostructures based on Nb and permalloy $(\mathrm{Py}:{\mathrm{Fe}}_{20}{\mathrm{Ni}}_{80})$. By measuring the magnetic moment as a function of the temperature in S/F/S trilayers for different thicknesses of the middle F layer, we give evidence of the presence of a magnetic stray field of the F layer. For values of F-layer thickness below a threshold, we establish a correlation between the magnetic measurements of the S/F/S trilayers and the anomalous magnetic dependence of the critical current in S/Insulator/thin superconducting film/F/S (SIsFS) Josephson junctions (JJs). These complementary investigations provide a self-consistent method to fully characterize S/F heterostructures and possibly demonstrate effects arising from the mutual interactions between ferromagnetism and superconductivity. A shift in the Fraunhofer critical current oscillations has been observed in the opposite direction to the one commonly observed in JJs with F barriers, as it has been recently predicted by inverse and electromagnetic proximity theories. This inverse memory effect is relevant for the design of these heterostructures as memory cells and spintronic devices.

Electrical Conditions in 3-phase Submerged Arc Furnaces: Learning from the ElMet Project

ElMet is the short name for a competence project (2015-2020) on electrical conditions in 3-phase submerged arc furnaces (SAFs). In the project, NORCE has cooperated closely with The Norwegian University of Science and Technology (NTNU), University of Oxford, University of Santiago de Compostela, and the industrial partners, Elkem and Eramet Norway. ElMet has focused on mathematical modelling, and a set of tools have been utilized: • Basic equation analysis, together with very simplified models, have clarified fundamental aspects. • 2D and 3D models have then supplied important overall insight. • Finally, metamodels have enabled a link between physics- and data-based modelling. The ElMet project has established a sound basis for understanding electrical conditions in SAFs, and proper tools have been developed and tested for future use: • Flexible 3D simulations models to be applied for various case studies. • A strong electromagnetic proximity effect for (almost) parallel currents has been discovered. • Induced currents in the furnace steel shell carry information that might be utilized for identification of inner conditions. • Metamodels, together with additional measurements, seem suitable for on-line use and to identify inner furnace conditions.

Вплив електромагнетного ефекту близькості на транспортні характеристики джозефсонівських переходів феромагнетик/надпровідник–бар’єр–надпровідник

Вплив електромагнетного ефекту близькості на транспортні характеристики джозефсонівських переходів феромагнетик/надпровідник–бар’єр–надпровідник

Improving the performance of a patch antenna array by using photonic bandgap structures at X-band

A proposed three-layered patch antenna array combined with Uniplanar Compact Photonic Bandgap structures (UC-PBG) is presented to avoid non-desired radiations from the feeding structure and to mitigate the surface propagation modes, increasing the radiation efficiency, and reducing the parasitic lobes. The array is fed by electromagnetic proximity, implemented by a stripline network below the radiators. The array is designed to operate at of 10 GHz and is surrounded by UC-PBG structures. This configuration also helps to increase the bandwidth by keeping the electric field and the surface current stable around the radiators, reducing the variations of the impedance on a wider bandwidth. Also, the UC-PBG structures attenuate the surface propagation modes, lowering the parasitic lobes by almost 7 dB and reaching measured radiation efficiency higher than 80%. The patch array gets an operational bandwidth of 2.5 GHz, with a measured gain of 24 dB. The fractional bandwidth is 25%.

Piece‐wise control of constant electromagnetic moments for spacecraft self‐ and soft‐docking exploiting dynamics conservation

AbstractInter‐spacecraft electromagnetic proximity operation has many potential advantages, such as no propellant consumption and plume contamination, while providing high‐precision, continuous, reversible, synchronous, and non‐contacting control capability. In addition, with constant magnetic moment actuation, the inter‐spacecraft electromagnetic force is, in essence, a kind of conservative force and has dynamics conservation. This yields specific and targeted evolvement laws of relative motion among these actuated magnetic dipoles. Exploiting these properties, spacecraft self‐ and soft‐docking could be achieved with proper piece‐wise constant magnetic moments design, which not only improves control precision, but also reduces the demand of relative motion measurement and simplifies docking controller design. Aiming at electromagnetic spacecraft self‐ and soft‐docking controller design, this paper uses dynamic modeling and dynamics conservation analysis to derive the specific evolvement laws of relative motion between the actuated magnetic dipoles first, and then utilize these laws and corresponding dynamics conservation to design the piece‐wise constant electromagnetic moments.

Design of the Electric Control System for the Cleaning Equipment of Pigsties

According to the control requirements of cleaning equipment, this paper designs corresponding electrical control system the design detection system is designed to realize horizontal and vertical positioning of cleaning mechanism with electromagnetic proximity switches. The control circuit is designed with a VB1 model PLC as main controller, the system control flow is analyzed to switch the steps of entering a pigsty, collecting pig manure, and returning and dumping pig manure.

Manifestation of the electromagnetic proximity effect in superconductor-ferromagnet thin film structures

Using the newly emerged theory model of an electromagnetic proximity effect, we demonstrate that it provides a good description of our previously reported anomalous Meissner screening observed in thin film superconductor-ferromagnet proximity structures. Using the low energy muon spin rotation measurement technique, we further investigate this new theory by probing directly the flux screening in various superconductor-ferromagnet proximity structures. We examine its main characteristics and find in general good agreement between theory and experiment. Understanding and control of this new proximity effect is an important step forward toward a new generation of superconducting spintronic devices.

Controlling the electromagnetic proximity effect by tuning the mixing between superconducting and ferromagnetic order

We present low-energy muon-spin rotation measurements on $\mathrm{Cu}/\mathrm{Nb}/{\mathrm{AlO}}_{x}/\mathrm{Co}$ thin films that probe the newly described electromagnetic (EM) proximity effect. By varying the thickness of the insulating ${\mathrm{AlO}}_{x}$ layer we control the degree of coupling between the superconductor and ferromagnet and thus the EM proximity effect. For barrier thicknesses up to 4 nm we find both a small contact-dependent reduction in the standard Meissner effect and a larger diamagnetic contribution originating at the $\mathrm{Nb}/{\mathrm{AlO}}_{x}/\mathrm{Co}$ interface which decays away over a lengthscale far exceeding the superconducting coherence length. This second component we attribute to the EM proximity effect. Our analysis provides compelling experimental evidence for previously neglected electromagnetic effects within proximity coupled systems.

Electromagnetic proximity effect controlled by spin-triplet correlations in superconducting spin-valve structures

The spin-triplet correlations in superconducting spin valve structures arising in the presence of noncollinear textures of magnetic moment are shown to enhance strongly the electromagnetic proximity effect, i. e. the long-range leakage of the magnetic field from the ferromagnet (F) to the superconducting (S) layer. Both the dirty and clean limits are studied on the basis of the Usadel and Eilenberger theory, correspondingly. Our results suggest a natural explanation for the puzzling enhancement of the spontaneous magnetic fields induced by the noncollinear magnetic structures observed by the muon spin rotation techniques in a wide class of layered S/F systems. We show that the electromagnetic proximity effect causes the shift of the Fraunhofer dependence of the critical current on the external magnetic field in the Josephson junction with one superconducting electrode covered by the ferromagnetic layer. This provides an alternative way to measure both the magnitude and the direction of the spontaneous magnetic field induced in the superconductor. We also demonstrate the possibility of the long ranged superconductivity control of the magnetic state in F$_1$/S/F$_2$ structures.

Investigation of the influence of a large steel plate on the magnetic field distribution of a magnetic proximity detection system.

A magnetic proximity detection system is mounted on a mobile mining machine to prevent underground workers from being pinned or struck by machine motion. The system generates magnetic fields around the machine to determine safe working distances. The miner-worn component measures the magnetic field in order to approximate location. Large masses of steel, such as those from mining equipment, can alter the magnetic field distribution. This affects the locational accuracy of the system, thus adversely impacting worker safety. To examine this problem, U.S. National Institute for Occupational Safety and Health researchers developed a method and test system to study the influence of a steel mass on the magnetic field distribution. The results show that a steel plate can strengthen the magnetic field perpendicular to the generator by up to 40 percent. Furthermore, they show that the degree of the influence on the field distribution is a function of distance. The results from this study can be used to further develop and improve the performance and reliability of electromagnetic proximity detection systems used in underground mining applications.

The adoption and implementation of RFID : a literature survey

INTRODUCTIONRFID is being used for a wide variety of applications ranging from building access control proximity cards to supply chain tracking, toll collection, vehicle parking access control, retail stock management, ski lift access, library books tracking, theft prevention, vehicle immobilizer systems, and railway rolling stock identification and movement tracking. This paper reviews the literature on the use of RFID in library management and service through an innovation decision framework. We provide a brief introduction to the RFID technology, current challenges faced by libraries, and how the use of RFID technology can address these challenges. Next, we analyze the specifics of RFID technology in different areas of library management and services before examining the potential benefits of RFID, and identifying barriers to its acceptance. Finally, we propose a critical success factor framework for RFID implementation based on the publications reviewed and provide guidance for librarians.RFID technology is widely used in libraries. However, the number of published papers on the use of RFID technology in libraries lags behind the number of papers on its use in supply chain. Mehrjerdi (2011) reviewed the implementation of RFID technology in libraries, and suggested developing RFID technology for library search. RFID has revolutionized library management and practices. According to the Singapore National Library Board, most libraries in Singapore are aggressively using RFID technology, resulting in 9 million books, videos and DVDs being embedded with antitheft chips and allowing for self-checkout. In Australia, Brisbane City Council's libraries have used an RFID system at their Wynnum branch since June 2001 (Cadoo, 2004). Successful implementation and use of RFID technology is also evident in the United States, United Kingdom, Canada, South Korea and New Zealand.OVERVIEW OF THE RFID TECHNOLOGYRFID is one of the Automatic Identification and Data Capture (AIDC) technologies. The purpose of such technologies is to identify objects, automatically collect data about the objects and update the data into a computer system without human intervention (Potdar, Wu & Chang, 2010). RFID is an electronic information technology that utilizes wireless radio waves to transmit, identify, trace, sequence and confirm various objects (Liu & Chen, 2009; Roberts, 2006). It can be characterized as an electromagnetic proximity identification and data transaction system (Roberts, 2006). Two components in RFID are the tag and reader. RIFD tags are used to tag objects or assets, and an RFID reader gathers the tag information. RFID technology is a replacement for barcode technology in terms of non-optical proximity communication, information density and two-way communication. Compared to barcode technology, RFID technology possesses powerful properties which include being waterproof, having a magnetic scratch-resistant protection layer, being heat resistant, being long lasting, transmitting data transmission over long and short distances, data encryption, and relatively large memory capacity (Bi, Cao & Sheng, 2011). RFID technology is also more powerful than other AIDC technologies such as cameras, magnetic cards and identity card because of its data read and write functions, easy miniaturization and diversification of the shape, environmental resistance, reusability, data penetration, data memory capacity, system security and data security.RFID uses several common methods of identification, but the most common method is the association of the RFID tag unique identifier with an object or person. The basic concepts in RFID diagram typically comprise the following (Ramanathan, Ramanathan, Wan & Ko, 2014):1. An RFID device (tag)2. A tag reader with an antenna and transceiver3. A host system or connection to an enterprise system.RFID devices can be divided into two categories:1. …

Thermal Characterization of Electrical Wires and Insulation Operated in Variable Frequency Mode

NFPA 70 provides guidelines on conducting wire size rating for different service current ratings. Additionally, an engineering calculation method is provided for unusual cases. While not apparent, these guidelines are valid only for 60 Hz type frequencies. Electrical conductors have increased Joule heating with higher frequency operation because of electromagnetic effects like skin and proximity effects and the increase of total reactance of conductors and appliances. Until now, those effects have not been a fire safety concern, but the large increase in high power applications using frequencies higher than 60 Hz in variable frequency drives, also called adjustable frequency drives or simply “AC drives”, to control the operation of large motors, changes this. While research has improved the performance of motors and AC drives, there has been relatively little research on the thermal effects and fire safety implications of these systems. In this paper we show that conductors used with common variable frequency power electronics have heat dissipation rates that can be up to 50% larger than what is calculated according to the standard formulas used for 60 Hz systems. Using accelerated aging models for the wire insulation it is shown that these increases in heat dissipation rate can reduce useful cable life by a factor of two or more.

A Visual Warning System for the Identification of Proximity Detection Events around a Continuous Mining Machine

Underground mobile mining machines pose a difficult safety challenge since their operators generally work in close proximity to these machines in very restricted spaces. Intelligent software for use with electromagnetic proximity detection systems has been developed that can accurately locate workers around mining machinery in real time. If a worker is located too close to the machine, the machine’s operation can be partially or completely disabled to protect the workers from striking, pinning, and entanglement hazards. Researchers have developed a visual method of relaying to the operators the interdiction of their machine operations by this intelligent proximity detection system. Several lighting sequence scenarios were human subject tested for effectiveness using a computer-based multimedia platform. Analysis of the test results indicates that a “fast flash” lighting arrangement is the most effective scenario based upon subject preference, rating, and accuracy of proximity intrusion location identification. This arrangement improves reaction time by 35%.

Thermal Impacts of Electromagnetic Proximity Effects in Induction Cooking System With Distributed Planar Multicoils

This paper investigates the thermal impacts of electromagnetic proximity effects among the coils of domestic induction heating system (DIHS) with distributed planar spiral multicoils. A combined coordinates system is developed in the computation, consisting of a master Cartesian coordinate system and multiple slave cylindrical coordinate systems. The proposed computing method is implemented with different effecting parameters so as to analyze the impacts of proximity effects and eddy currents distribution in the DIHS. Computation results are validated through comparing against those from the finite element method (FEM). Furthermore, the temperature field is calculated to study the thermal impacts of proximity effects on the thermal distribution in the induction plate.

Shaky Hand: A Novel Laboratory Demonstrator

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The Shaky Hand system is a new, visually appealing laboratory demonstrator. It is presented as a novel concept for use in control education—as an effective combination of mechanical and electronic hardware, firmware and software. Based on a simple village fête game, the aim is to guide, under feedback control, a wire loop along a meandering wire track from one end to another, without touching the loop to the track. The system utilizes a set of electromagnetic proximity sensors to locate and follow the track. This paper describes the mechanical and electrical components that make up Shaky Hand, and the control strategy that is used to effect successful control action. Shaky Hand is also implemented in simulation, and the paper describes the mathematical modelling. </para>

Lithographic qualification of new opaque MoSi binary mask blank for the &lt;inline-formula&gt;&lt;math display="inline" overflow="scroll"&gt;&lt;mrow&gt;&lt;mn&gt;32&lt;/mn&gt;&lt;mtext&gt;-&lt;/mtext&gt;&lt;mi&gt;nm&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/inline-formula&gt; node and beyond

We discuss the lithographic qualification of a new type of binary mask blank consisting of an opaque layer of MoSi on a glass substrate, referred to simply as OMOG. First, OMOG lithographic performance will be compared to a previous chrome/MoSi/glass binary intensity mask (BIM) blank. Standard 70-nm chrome on class (COG) was not considered, as it failed to meet mask-making requirements. Theory and a series of simulation and experimental studies show OMOG to outperform BIM, particularly due to electromagnetic effects and optical proximity correction (OPC) predictability concerns, as OMOG behaves very similarly to the ideal thin mask approximation (TMA). A new TMA-predictability metric is defined as a means to compare mask blanks. We weigh the relative advantages and disadvantages of OMOG compared to 6% attenuated phase shifting. Although both mask blanks are likely sufficient for the 32-nm and 22-nm nodes, some differences exist and are described. Overall, however, of the blanks considered, it is concluded that OMOG provides the most robust and extendable imaging solution available for 32-nm and beyond.