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Conventional electronic article surveillance (EAS) tags are ineffective on metallic packaging. The component of the RF magnetic field perpendicular to the surface of the packaging induces eddy currents that suppress the magnetic flux, linking the inductive element of the tag. In this article, an inductive quarter-wavelength planar cavity, formed by wrapping aluminum foil around a ferrite core, was extended by wrapping additional capacitive layers of foil/dielectric around the ferrite-filled central region. This so-called wrapped tag exhibits the frequency, $Q$ -factor, and read distance characteristics of existing EAS tags, but is instead driven by the RF magnetic fields parallel to the surface of the metallic packaging. In this article, we compare the observed frequency response of the wrapped tag with a simple LC resonator model that considers the tag’s geometrical features, and use the model to describe how the design and construction of the tag can be optimized. Finite-element method (FEM) modeling is used to reveal how the current flows in the wrapped foil of the tag. Prototype tags show good reproducibility, demonstrating the potential of the design as a solution to the problem of tagging metallic packaging in the EAS industry. [ABSTRACT FROM AUTHOR]

This paper investigated the magnetic properties of novel soft magnetic composite (SMC) with ferrite nanofibers. Material consists of FeSi powder covered by resin and different amounts of Ni0.3Zn0.7Fe2O4ferrite nanofibers. We prepared SMC with very high specific electrical resistivity. FeSi/resin (0.49 wt% ferrite) sample exhibits the highest electrical resistivity ($6.05~\Omega \cdot \text{m}$) due to low interparticle contacts. The image analysis of SEM pictures was used for the evaluation of effective area, in which local eddy currents are flowing. The FeSi/resin (0.49 wt% ferrite) sample displays the lowest total losses in the measured frequency range due to the highest specific electrical resistivity and appropriately covered FeSi particles. Loss separation and the analysis of movable magnetic objects were performed for all studied materials. [ABSTRACT FROM AUTHOR]

The maximization of bandwidth in broadband magnetic devices, done reliably in mass production, has led to a strong industry interest in substrate embedded ferrite core materials with windings fabricated by photolithography. Ferrites, when embedded within a substrate, can lose significant magnetic permeability due to stress from the cured bonding adhesive. In this paper, an experimental survey is conducted, encapsulating sample ferrites in various types of bonding adhesive and measuring the change in the ferrite core’s inductance. The adhesives include epoxies, cyanoacrylates, polyurethanes, and silicone sealants, and each adhesive is evaluated on curing procedural limitations, bonding strength, and resulting loss in inductance when used as a ferrite encapsulant. Though tradeoffs exist, the best choice based on bonding strength and minimal loss of inductance was found to be a low shrinkage, rigid epoxy. [ABSTRACT FROM PUBLISHER]

This paper investigates the partial irreversible demagnetization characteristics of magnets in flux-switching permanent magnet (FSPM) machines. Two different partial demagnetization mechanisms in the FSPM machines are modeled and demonstrated. The 2-D finite-element analysis (FEA) results for a baseline 10 kW 15 kr/min ferrite FSPM machine verify the validity of the proposed partial demagnetization model. Performance degradation due to demagnetization is evaluated for the baseline machine based on the FEA results. This paper also proposes a novel design to enhance the demagnetization withstand capability. This research reveals the most vulnerable region of the magnet to irreversible demagnetization in the FSPM machines. It also provides a guideline for developing demagnetization withstand capability improvement techniques. [ABSTRACT FROM PUBLISHER]

We have developed a scanning magnetic microscope (SMM) based on a magnetic tunneling junction (MTJ) magnetoresistive (MR) sensor. The microscope is based on commercially available components employing two sets of scanning stages and a MTJ sensor. Spatial resolution and noise sensitivity were investigated using two MTJ sensors, one having high spatial resolution and the other low noise but coarser spatial resolution. We present measurements of magnetic field images from ferrite concentration calibration standards and a stainless steel welded specimen both imaged using a magnetoresistive scanning microscope. A sensitivity of \sim 10\ \muT/FN was obtained from standards with defined ferrite numbers (FN). This microscope represents a new powerful tool for the characterization and investigations of delta ferrite concentrations in stainless steel welded samples. [ABSTRACT FROM PUBLISHER]

This paper explores an influence of conductive layer geometry on electrical parameters of ferrite electromagnetic interference (EMI) suppressor, which consists of conductive layer in ferrite monolithic structure. Near ferrimagnetic resonant frequency, component has maximal impedance and efficiently suppresses noise. In order to achieve better suppression (i.e., larger impedance), conductive layers should be longer. Nevertheless, longer conductive lines introduce parasitic capacitance, which causes the maximal impedance frequency shift. Because of that, the frequency range where component can be used for efficient EMI suppression is shifted towards lower frequencies, and designing process should be very careful. In this paper, we present simulation of frequency dependent impedance for different geometry parameters of conductive layer. Results for the inductance and the maximal impedance frequency shift of the proposed EMI suppressors are presented in the range 1 MHz-3 GHz. Proposed EMI suppressors were experimentally tested using Agilent 4287A RF LCR meter. Comparison of simulated and measured values of impedance shows a good agreement. [ABSTRACT FROM AUTHOR]

The goal of this work was to investigate the behavior of a ferrite electromagnetic interference (EMI) suppressor when placed in a real surrounding. Electrical parameter measurements of the same EMI suppressor can differ for different combination of instruments and test fixtures. For that reason specially designed microstrip test fixtures are developed for the vector network analyzer (VNA) measurements. This paper describes the measurement technique, parameters extraction, and characterization of ferrite EMI suppressors for printed circuit board (PCB) applications. Two commercially available components, multilayer chip SMD inductors in a ferrite body, are measured and characterized using a VNA E5071B and developed adaptation test fixture on PCB board. These measurements describe intrinsic and extrinsic parameters of the components and their behavior. If the components are mounted on the PCB, i.e., in a real environment, then the two-port EMI suppressor model with extrinsic parameters has to be used at RF frequencies. The comparison of measured and datasheet values is further presented. [ABSTRACT FROM AUTHOR]

Switch mode power supplies are the predominant form through which power conversion is currently implemented in electronic equipment. Within such power supplies, ferrite cored magnetic components are commonly placed under dc bias conditions which, due to magnetomechanical effects, can result in higher than expected core losses. This paper presents measurements that show the impact of magnetomechanical effects on the losses of a MnZn ferrite core material under low ac excitation and high dc bias conditions. The measurements are made using an accurate measurement circuit, and the results show the impact on losses of magnetomechanical resonance. In addition distorted, figure-eight shaped B-H loops are measured, which are also believed to manifest from magnetomechanical interactions. These B-H loops show that, on a transient basis, magnetomechanical interactions may take place in a manner that is not only lossless, but returns energy back to the excitation supply. [ABSTRACT FROM AUTHOR]

It is well known that the measurement of ferrite core losses is difficult, particularly under low power factor conditions for which the excitation VA drawn is large relative to the power dissipated in the ferrite core. This paper proposes a new technique, called mutual inductance neutralization, which overcomes this difficulty by compensating for the reactive power drawn by the circuit through the use of an air cored mutual inductor. Based on the technique, circuits are presented which are appropriate for core loss measurement in the absence, and the presence of a dc bias. Measured results are presented which verify the accuracy of the technique, and results are also presented showing the effect of dc bias conditions on the losses of the ferrite core under test. [ABSTRACT FROM AUTHOR]

A novel coplanar waveguide ferrite-coupled line (CPW FCL) is presented and numerically verified for the first time. The proposed CPW FCL exhibits a low insertion loss for both even and odd mode excitations, equal power division for single power excitation with both isolation, and return loss better than 10 dB over the whole operating bandwidth, and 20 dB in the best cases. The coupler has a much wider operation bandwidth compared to any other configurations reported to date. In addition, the .CPW FCL demonstrates better phase flatness within the operating bandwidth compared to microstrip FCL. [ABSTRACT FROM AUTHOR]

In switched-mode power supplies—the predominant type of power converter in contemporary electronic equipment—ferrite magnetic components under dc bias conditions are typically large and have relatively high losses. The nature of these losses is not widely understood, and research in this area has been hampered by the difficulty of obtaining accurate core loss measurements. This paper reviews previous studies on the nature of core losses under dc bias, and presents new results, measured by a technique that has not previously been utilized for the measurement of core losses under dc bias conditions. The results show that ferrite core losses increase significantly with an increasing dc bias, and highlight the need for further research over a wider range of conditions to fully characterize the phenomenon. [ABSTRACT FROM AUTHOR]

This paper considers high-frequency (200 kHz-1.0 MHz) losses in MnZn power ferrites and shows that none of the three well-known magnetic loss mechanisms (namely, hysteresis, classical eddy-current loss, and excess eddy-current loss) can account for the experimentally observed dependence of the loss on the frequency and flux density. In order to investigate the origin of this discrepancy, the electric field that is induced in the typical core when the material is driven at high frequencies and flux densities was estimated. The estimates show that these electric fields can be quite large. The paper presents experimental data on the electrical conductivity for such large electric fields, which shows a highly nonlinear behavior that can give rise to a modified eddy-current loss mechanism. By a simple curve fit to the nonlinear conductivity, the experimentally observed flux density dependence of the high-frequency loss, which previously could not be explained, can be reproduced by using this modified eddy-current loss mechanism. A modified ferrite structure can eliminate most of these extra losses by reducing the electric field generated at the grain boundaries due to high frequencies and flux densities. [ABSTRACT FROM AUTHOR]

In this paper design, modeling and characterization of single and double coils, which consist of conductive layer embedded in the soft ferrite material, are described. These surface-mount components, comprising of a cofired multilayered ferrite and coil, have been developed in the ceramic coprocessing technology. A simple analytical model of proposed structures is presented. This model is very suitable for circuit simulations and for prediction of frequency characteristics of considered inductors. The inductance and impedance of coils embedded in low permeability or high permeability ferrite material are calculated and compared. Also, these suppressors were experimentally tested in the frequency range 1 MHz-3 GHz using an Agilent 4287 A RF LCR meter. The calculated results were in good agreement with the measured ones. [ABSTRACT FROM AUTHOR]

This paper deals with the characterization of dynamic loops shapes and losses in soft magnetic materials. An experimental and theoretical analysis has been done in order to describe static and dynamic hysteresis on soft ferrite cores. A parallelogram-loop-based hysteresis modeling is described and discussed. The possibility of the model to include vector hysteresis and the related properties are then discussed, with particular attention to the case of a rotating magnetic field into an isotropic and anisotropic medium. [ABSTRACT FROM AUTHOR]

This paper presents a derivation of expressions for the electromagnetic fields propagating at a frequency near gyromagnetic resonance on a ferrite cylinder magnetized by an applied axial dc magnetic field. This system allows propagation by hybrid surface waves only, where the axial electric and magnetic fields are both nonzero. The expressions apply to the transverse impedance, the ratios of the electric field to the magnetic field for the radial and azimuthal components of these waves, and the power transfer impedance, which relates the axial current to the power transferred by these waves. Numerical values, based on the properties of strontium hexaferrite measured at 120 GHz, show that the power transfer impedance may exceed 1 MΩ. The data suggest that short lengths of such high-impedance transmission line could be used to increase the output from millimeter-wave mixers. [ABSTRACT FROM AUTHOR]

We investigated the complementary effects of TiO2 and MoO3 additives on the magnetic properties, the core loss, and the dielectric properties of MnZn ferrites. We analyzed the composition factors influencing the penneability of MnZn ferrites. A high initial penneability base ZnO-MnO-Fe2 O3 composition ratio was selected. Electrical and dielectric analyses indicated that the introduction of TiO2 can improve the high-frequency loss properties of MnZn ferrite cores, but such introduction will also have a negative effect on the magnetic properties of the sintered sampies. Introduction of MoO3 can alleviate the negative influence of TiO2 and also reduce the internal polarization intensity. As a result, the dielectric constant and corresponding dielectric loss may be reduced. We give experimental results in the paper. [ABSTRACT FROM AUTHOR]

We investigated the complementary effects of TiO2 and MoO3 additives on the magnetic properties, the core loss, and the dielectric properties of MnZn ferrites. We analyzed the composition factors influencing the penneability of MnZn ferrites. A high initial penneability base ZnO-MnO-Fe2 O3 composition ratio was selected. Electrical and dielectric analyses indicated that the introduction of TiO2 can improve the high-frequency loss properties of MnZn ferrite cores, but such introduction will also have a negative effect on the magnetic properties of the sintered sampies. Introduction of MoO3 can alleviate the negative influence of TiO2 and also reduce the internal polarization intensity. As a result, the dielectric constant and corresponding dielectric loss may be reduced. We give experimental results in the paper. [ABSTRACT FROM AUTHOR]

We suggest a practical approach for modeling frequency-dependent losses in ferrite cores for circuit simulation. Previous work has concentrated on the effect of eddy-current losses on the shape of the B-H loop, but in this paper we look at the problem from the perspective of energy loss and propose a different network for accurately modeling power loss in ferrite cores. In power applications, the energy loss across the frequency range can have a profound effect on the efficiency of the system, and a simple ladder network in the magnetic domain is not always adequate for this task. Simulations and measurements demonstrate the difference in this approach from the ill ladder network models both in the small-signal and large-signal contexts. [ABSTRACT FROM AUTHOR]

Presents a study that examined magnetic flux distribution and iron loss distribution in ferrite cores under pulse excitation using the finite element method. Background on the use of manganese-zinc ferrite cores in the transformers of switching power supplies; Analysis of magnetic characteristics under pulse excitation; Results and implications.

Focuses on a study which proposed a microwave and thermal method to model high-power ferrite devices. Description of the microwave finite-element analysis; Discussion on the operating regions of magnetic loss that must be avoided; Investigation of the thermal characteristics of a differential phase shift ferrite-loaded waveguide; Calculations for selected bias field.

Magnetic (static, high-frequency) and microwave-absorbing properties of Co-substituted [Ni.sub.2]W hexaferrites are investigated in the frequency range of Ka-band (26.5-40 GHz). The powders of composition Ba[Ni.sub.2-X][Co.sub.X][Fe.sub.16][O.sub.27] are prepared by calcining at 1250[degrees]C, where the substitution ratio x was varied from 0.0 to 1.4. With the calcined powders, the composite specimens are prepared using the silicon rubber as a matrix material. Vibrating sample magnetometer measurement indicates that the coercivity of the specimens of Ba[Ni.sub.2-X][Co.sub.X][Fe.sub.16][O.sub.27] decreases with Co substitution, which is attributed to a reduction of crystal anisotropy field by changing the easy-axis of magnetization from c-axis to basal plane. The complex permeability spectrum shows the decrease of resonance frequency with Co substitution. The specimens with composition of x = 0.2 and x = 0.4 show the superior microwave absorbing properties in Ka-band. For the specimen of x = 0.4, the bandwidth (with respect to--20-dB reflection loss) is 26.5-32 GHz at a matching thickness of 0.9 mm. The Co substituted [Ni.sub.2] W-hexaferrites can, therefore, be suggested as a good absorbing material for the electromagnetic radiation in the frequency range of Ka-band. Index Terms--Absorber, hexaferrite, Ka-band, [Ni.sub.2]W.

An integrated inductor using the low-temperature co-fired ceramics (LTCC) technology for low-power electronics was fabricated The inductor has Ag circular spiral coil with 16 turns (2 turns × 8 layers), a dimension of 11.52 mm in diameter, and 0.71 mm in thickness. To establish the calculation of inductance, including total resistance, the fabricated inductor was analyzed. It was confirmed that the calculated values were very close to the measured values. Finally, a low-profile ferrite core, with parameters at μR = 2400 and AL value = 4000 nH/mm², was applied to the inductor to increase inductance. As a result, inductance increased by 293%, compared to the uncored inductor. [ABSTRACT FROM AUTHOR]

A new wideband common-mode noise filter for switching power supplies has been developed. The filter consisted of an Mn-Zn ferrite core and a copper/polyimide tape wound coil. The tape wound coil had two signal lines, two ground lines, and a poly- imide dielectric film. The filter exhibited a common-mode rejection of over 30 dB in the wide frequency range of 100 kHz to 100 MHz. The wideband common-mode filtering was due to the high-frequency magnetic loss of the Mn-Zn ferrite core and the optimum ground point selection for the ground lines. [ABSTRACT FROM AUTHOR]

A numerical method to obtain nonuniform field distribution in magnetic substrates is presented. The method is applicable to different geometries and it is not restricted to uniform applied fields. The only assumption is that the local internal field is high enough so the material is saturated and at all points the magnetization is parallel to the local internal field. [ABSTRACT FROM AUTHOR]

Two types of magnetic tape were produced by oblique sputtering with the incident angle of 65±5°. One consists of a 180-nm Cr underlayer layer and 20-nm Co layer. The other consists of a 90-nm NIAI seed layer, 90-nm Cr intermediate layer, and 20-nm Co layer. It is shown that the use of NiAI seed layer allows further reduction of the Co grain size and improves the film smoothness. The fine microstructure obtained in the NiAl seed layer resulted in smaller Co grains with more uniform size distribution. This caused the switching field distribution to become narrower, while the values of the squareness and coercivity remained high. The recording performances were also improved for the tape with N1Al seed layer. [ABSTRACT FROM AUTHOR]

Iron spheres 2.0 μm in diameter in distilled water was successfully encapsulated in dense Ni-Zn ferrite layer 15-20 mu thick by simplified ferrite plating method. In this method, a reaction solution of FeCI2 + NiCl2 + ZnCl2 and a pH adjusting solution of KOH were added to the water. The solution was stirred at 25°C in open air. The dissolved oxygen worked to oxidize a part of Fe2+ to Fe3+. The deposited Ni-Zn ferrite layer on Fe micro- sphere surface was composed of fine grains 10-15 nut in diameter. Since the Ni-Zn ferrite layer was very thin and dense, a large saturation magnetization M5 = 210 emu/g, almost the same as that of bare Fe, was obtained. The compacted cores of these Fe/ferrite mi crospheres exhibited excellent frequency characteristics exceeding Snoek's limit for Ni-Zn ferrite cores by factor 4. [ABSTRACT FROM AUTHOR]

We have developed a permanent magnetic pavement marking tape. Sections of varying magnetization wavelength were installed in a 230-m linear array. Magnetic field profiles were determined at lateral displacements from the tape out to 0.9 m. Calculations based on a surface pole model with no adjustable parameters gave excellent agreement with the experimental results. [ABSTRACT FROM PUBLISHER]