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Magnetics, IEEE Transactions on

Issue 5 • Date May 2006

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Displaying Results 1 - 25 of 25
  • [Front cover]

    Publication Year: 2006 , Page(s): c1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2006 , Page(s): c2
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  • Table of contents

    Publication Year: 2006 , Page(s): 1493 - 1494
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  • Influence of grain boundaries and voids on the saturated magnetization in Fe3O4 films at a low magnetic field

    Publication Year: 2006 , Page(s): 1495 - 1498
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1296 KB) |  | HTML iconHTML  

    We report the magnetic behaviors of Fe3O4 thin films grown by zero field growth (ZFG) and field growth (FG) techniques during the sputtering process. In FG conditions, an in situ 300 Oe field during growth is applied to a substrate, inducing an easy axis of magnetization. Structural observations obtained by high-resolution transmission electron microscopy measurements clearly depicted a significant reduction of the grain boundaries and voids in the Fe3O4 films grown under FG conditions, thus explaining the saturated magnetization of the Fe3O4 films at about 0.01 T. This behavior was expected due to a remarkable reduction of the antiferromagnetic exchange couplings between grains for FG conditions. In addition, the zero-field-cooled magnetization of the ZFG samples showed an abrupt change at about 285 K, confirming the existence of defects or other phases in the ZFG films. View full abstract»

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  • Pressure dependence of magnetoresistance for Fe/Cr multilayers

    Publication Year: 2006 , Page(s): 1499 - 1502
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    The magnetoresistance (MR) in Fe/Cr magnetic multilayers (MML) has been measured under high pressure up to 2.5 GPa. It is found that the spin-dependent scattering plays an important role in the pressure dependence of MR ratio. In the present work, for [Fe(20Å)/Cr(10 Å)]20 MML with antiferromagnetic (AF) state, the pressure coefficient of saturation field Hs is (1/Hs)(∂Hs/∂P)=3.3×10-2 GPa-1 between 0.1 and 2.5 GPa. We found that the (1/|J|)(∂|J|/∂P) for AF-Fe/Cr MML with polycrystalline structure is opposite in sign to that with epitaxial one. For [Fe(20 Å)/Cr(22Å)]20 MML with ferromagnetic (F) state, anisotropic magnetoresistance (AMR) decreases with increasing pressure. It is suggested that the anisotropy constant decreases with weakening spin-orbit interaction at high pressure. At high field, the AMR is easily suppressed by applying pressure while the giant magnetoresistance around Hs increases slightly with increasing pressure for polycrystalline Fe/Cr MML. View full abstract»

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  • Finite formulation of nonlinear magnetostatics with Integral boundary conditions

    Publication Year: 2006 , Page(s): 1503 - 1511
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    This paper describes two hybrid methods coupling finite formulation of electromagnetic fields (FFEF) in a bounded domain to integral boundary conditions taking into account far field conditions. The two hybrid techniques use different boundary conditions: the first formulation is based on Green's function applied to magnetization source inside bounded domain while the other one is based on a boundary-element method on its external surface. Details about the coupling terms are given and handling of different magnetization sources is described, including the fictitious magnetization sources coming from nonlinear solutions. The proposed methods are validated versus different benchmark cases. Comparisons between the two techniques have been performed using different criteria (accuracy and convergence, memory requirements, etc.). View full abstract»

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  • Numerical Simulations of vector field distributions generated by circular permanent-magnet arrays with side-openings

    Publication Year: 2006 , Page(s): 1512 - 1517
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    In the rotary-magnetic refrigerator, a circular permanent-magnet array with side-openings (CPMAS) provides a magnetic field exceeding the remanence of each magnet. Here we show that the magnetic induction in the pole gap as well as inside the magnets of a CPMAS can be calculated using an analytical vectorial formula. The method is based on the representation of the field of a uniformly magnetized magnet by straight current-carrying wires on the surface of the magnet. The Biot-Savart law gives the vector field of a single wire of arbitrary orientation, position, and length; the sum of fields from each wire gives the total field. The magnetization hysteresis loop of the permanent magnet is included by varying the current density; this is then used to calculate modifications to the center field by demagnetization, including remanence inversion under the field generated by the CPMAS itself. The field analysis procedure described here can be used to optimize the structure of permanent-magnet arrays, especially for three-dimensional arrays of restricted or asymmetric geometry, for various applications. View full abstract»

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  • Efficient implementation of vector Preisach-type models using orthogonally coupled hysteresis operators

    Publication Year: 2006 , Page(s): 1518 - 1525
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    Vector hysteresis models are regarded as helpful tools that can be utilized in the simulation of multidimensional field-media interactions. Recently, substantial efforts have been focused on the refinement of vector Preisach-type models of hysteresis. The purpose of this paper is to present a computationally efficient vector Preisach-type hysteresis model constructed from only two scalar models having orthogonally inter-related elementary operators. Such a model is implemented via a linear neural network (LNN) fed from the outputs of discrete Hopfield neural network (DHNN) blocks having step activation functions. With this DHNN-LNN configuration, it is possible to carry out the identification process using well-established widely available algorithms. Details of the model, its identification, and experimental testing are presented. View full abstract»

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  • A genetic approach to solve numerical problems in the Preisach model identification

    Publication Year: 2006 , Page(s): 1526 - 1537
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3384 KB) |  | HTML iconHTML  

    This paper introduces an identification procedure of the classical and modified scalar Preisach models based on genetic algorithms. It can be used when a reduced set of experimental data is known. The main advantage of this approach is the numerical stability of the solution. The results show that the coupling between our genetic identification procedure and the modified scalar Preisach model is able to reproduce the experimental behavior of different magnetic soft steels. View full abstract»

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  • Trigonometric Integrals for the magnetic field of the coil of rectangular cross section

    Publication Year: 2006 , Page(s): 1538 - 1548
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    Formulas are derived giving the vector potential and the magnetic field components of a general coil of rectangular cross section and constant winding density. The solution is given in a cylindrical coordinate system in terms of trigonometric integrals. The formulas presented have been cross-checked and validated against alternative expressions giving the various field components as integrals of expressions containing Bessel and Struve functions. The trigonometric integrals for the fields can be evaluated easily to several hundred significant figures using mathematical packages such as Maple or Mathematica. Alternatively, they can be evaluated with a small FORTRAN program. Sample results and field line plots obtained with the method are given, and the field of a coil of rectangular cross section is examined in some detail. A comparison with the results of a finite-element method is also given. View full abstract»

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  • Magnetic field analysis by edge elements of magnetic components considering inhomogeneous current distribution within conductor windings

    Publication Year: 2006 , Page(s): 1549 - 1554
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    For magnetic field analysis by edge elements of the magnetic components, the method considering inhomogeneous current distribution within the conductor windings is investigated. To consider the inhomogeneous current distribution within the windings, we utilized the magnetic vector potential represented by edge elements and the current conservation equation represented by nodal elements in the region of the windings. In the first application, the eddy-current model, which has the conventional wire winding, was analyzed. For correct analysis using our method, it is required that all turns of the wire winding be divided into meshes. However, if the region of the wire winding does not exceed the winding window of the magnetic core, even the combination of our method and the solidly modeled wire winding enables us to correctly analyze the transformer and the inductor with conventional wire winding. In the second application, a flat transformer with conductor winding, such as a copper foil or sheet, was analyzed. The magnetic flux densities within the flat core and the inductance calculated by our method were in good agreement with the experiments. Thus, we confirmed the effectiveness of our method considering inhomogeneous current distribution within the conductor windings. View full abstract»

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  • Numerical analysis of low-frequency electromagnetic scattering from axially symmetric bodies using an inductance matrix

    Publication Year: 2006 , Page(s): 1555 - 1559
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    We have proposed a numerical method for calculating low-frequency electromagnetic scattering from axially symmetric conducting bodies with and without apertures. The surface of the perfectly conducting scatterer is modeled by a set of inductively coupled coil elements, and the current in each coil element is computed by solving an inductance matrix equation. A disadvantage of a conventional method for a scatterer with apertures is discussed. Scattering from various axially symmetric conducting bodies with or without apertures is calculated and the resulting fields are in good agreement with those obtained by finite-element method. View full abstract»

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  • A three-dimensional inverse finite-element method applied to experimental eddy-current imaging data

    Publication Year: 2006 , Page(s): 1560 - 1567
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB) |  | HTML iconHTML  

    Eddy-current techniques can be used to create electrical conductivity mapping of an object. The eddy-current imaging system in this paper is a magnetic induction tomography (MIT) system. MIT images the electrical conductivity of the target based on impedance measurements from pairs of excitation and detection coils. The inverse problem here is ill-posed and nonlinear. Current state-of-the-art image reconstruction methods in MIT are generally based on linear algorithms. In this paper, a regularized Gauss-Newton scheme has been implemented based on an edge finite-element forward solver and an efficient formula for the Jacobian matrix. Applications of Tikhonov and total variation regularization have been studied. Results are presented from experimental data collected from a newly developed MIT system. The paper also presents further progress in using an MIT system for molten metal flow visualization in continuous casting by applying the proposed algorithm in a real experiment in a continuous casting pilot plant of Corus RD&T, Teesside Technology Centre. View full abstract»

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  • Numerical models of volumetric insulating cracks in eddy-current testing with experimental validation

    Publication Year: 2006 , Page(s): 1568 - 1576
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB) |  | HTML iconHTML  

    This paper concerns fast electromagnetic modeling of volumetric cracks in conductive materials under eddy-current inspection. The underlying numerical method is described. The model is tested on cracks in aluminum structures employed in aeronautical manufacture. The computational results obtained with the method display satisfactory agreement with the respective experimental and numerical results obtained by representing cracks as nonconductive surfaces. View full abstract»

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  • Element-free galerkin method in eddy-current problems with ferromagnetic media

    Publication Year: 2006 , Page(s): 1577 - 1584
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    This paper focuses on the application of the element-free Galerkin method to the solution of eddy-current problems in ferromagnetic media. The method is first validated by comparison with an analytical linear solution, discussing the role of the numerical parameters that affect the solution accuracy. Then, the application is extended to nonlinear and hysteretic media, adopting the fixed point iterative scheme and the classical Preisach model. The proposed method is also tailored for nonhomogenous structures. The merits and drawbacks with respect to a finite-element approach are discussed for all the considered problems. View full abstract»

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  • A tunable magnetic inductor

    Publication Year: 2006 , Page(s): 1585 - 1590
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    For integrated radio-frequency applications, tunable magnetic inductors are expected. A tunable magnetic inductor, based on magnetoimpedance effect, is presented in this paper. The proposed inductor is constructed with a magnetic inductor body, wound by an insulated coil, inducing a longitudinal dc bias magnetic field when a dc control current is flowing through. Formed by a conductive core coated by a high-permeability magnetic layer, the magnetic inductor body can be realized by either a thin-film structure or a composite wire. The reluctance models for both thin-film and composite wire structures are studied. A prototype tunable magnetic inductor, using a composite wire element, has been characterized. The results show that by varying the dc control current, the inductance L of the magnetic inductor can be tuned. The tunable range depends on the frequency of the current flowing through the inductor. A relative variation of inductance ΔL/L0, up to 18% at low frequency (around 5 MHz), is achieved by applying a bias current of magnitude merely up to 15 mA. The quality factor varies from 5 to 17 in the measured frequency range. The proposed tunable inductor may be further optimized for high-frequency applications and has the potential to be realized in micro-electromechanical systems technology. View full abstract»

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  • Adjustable balancer with electromagnetic release of balancing members

    Publication Year: 2006 , Page(s): 1591 - 1596
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB) |  | HTML iconHTML  

    Adjustable balancers are useful in applications where rotational imbalance is frequently varied. For example, in media level servo track writers used in the hard disk drive industry, a set of blank disks is loaded on a spindle motor for the purpose of servo writing. Since servo writing is performed at high speeds, imbalance introduced by disks and spacers results in significant vibrations that can affect the quality of the servo writing process. This paper proposes a new configuration of adjustable balancer that enables to compensate for rotational imbalance each time a new set of blank disks is loaded into the servo track writing machine. The adjustable balancer is ring shaped with a number of grooves displaced around axis of rotation. Steel balls are placed inside the grooves and held by permanent magnets. Imbalance compensation is achieved by electromagnetically activated release of the steel balls. The main advantage of the proposed configuration is its large compensation range. Presented three-dimensional finite-element analysis results and experimental results demonstrate and prove the effectiveness of this novel configuration. View full abstract»

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  • Evaluation of superposition technique for calculating cogging torque in permanent-magnet brushless machines

    Publication Year: 2006 , Page(s): 1597 - 1603
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB) |  | HTML iconHTML  

    We evaluate the superposition method for calculating the cogging torque in permanent-magnet brushless machines, the resultant torque being synthesized from cogging torque components associated with a pair of magnets. Although finite-element analyses and measurements show that the resultant cogging torque cannot be synthesized directly from the torque components due to a single magnet, we use the concept of a fictitious single magnet to analytically establish the relationship between the cogging torque and key design parameters. The method is particularly useful in assessing the influence of the slot number and pole number combination. View full abstract»

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  • Real-time control of the 3-DOF sled dynamics of a -flux Maglev system with a passive sled

    Publication Year: 2006 , Page(s): 1604 - 1610
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    The real-time control of the three degrees of freedom (DOF) dynamics of an electrodynamic (EDS) Maglev vehicle is presented. The design is based on a 5-DOF state-space model of the sled dynamics that uses a simple algebraic model to describe the interaction between the -flux coils on the track and the permanent magnets on the sled. A first-order sliding mode controller with integral error term is used to control heave, pitch, and roll in real time from position-attitude information measured with sensors located on the sled. Experimental results show that control of the 3-DOF dynamics of the levitated vehicle in real time can be successfully achieved by the proposed method. View full abstract»

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  • Analytic three-dimensional response function of a double-shielded magnetoresistive or giant magnetoresistive perpendicular head

    Publication Year: 2006 , Page(s): 1611 - 1619
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB) |  | HTML iconHTML  

    Using the Fourier method, we have derived a three-dimensional, fully analytic model of a shielded magnetoresistive or giant magnetoresistive head for perpendicular replay. The head may include side shields. The field and the spectral response function are expressed in closed form. Here, we use the model to show the effect of varying the sensor-shield spacings and the air-bearing-surface-underlayer separation on the field and response of the sensor at high areal density. View full abstract»

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  • Transition shape analysis from medium noise measurements

    Publication Year: 2006 , Page(s): 1620 - 1625
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB) |  | HTML iconHTML  

    We present a technique to determine the transition shape in digital magnetic recording. The method involves analyzing both temporal and spectral transition noise measurements. This combined method simultaneously determines the transition parameter and the cross-track correlation width along with the transition shape. View full abstract»

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  • Cyclic redundancy check code based high-rate error-detection code for perpendicular recording

    Publication Year: 2006 , Page(s): 1626 - 1628
    Cited by:  Papers (13)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB) |  | HTML iconHTML  

    We present a particular generator polynomial for a cyclic redundancy check (CRC) code that can be used to detect all dominant error events in perpendicular recording over a broad range of densities. This polynomial is also effective in detecting error events that occur at codeword boundaries. The bit-error-rate and the sector-error-rate performances are validated that result from the use of the corresponding CRC code in conjunction with the well-known post-Viterbi error correction method. View full abstract»

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  • Intersymbol interference channels with signal-dependent non-Gaussian noise: estimation of achievable information rates

    Publication Year: 2006 , Page(s): 1629 - 1631
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB) |  | HTML iconHTML  

    In this letter, we calculate the achievable information rates for the intersymbol interference channels with general signal-dependent correlated noise under the constraint that the inputs are chosen from a finite alphabet. The proposed method employs canonical multivariate density estimation techniques. This method is important in that it can be used for accurate estimation of the achievable information rates for magnetic recording channels with media noise, where higher order media noise models can be taken into account instead of the first-order model. View full abstract»

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  • IEEE Magnetics Society & The IEEE Press call for books

    Publication Year: 2006 , Page(s): 1632
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    Freely Available from IEEE
  • IEEE Magnetics Society Information

    Publication Year: 2006 , Page(s): c3
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    Freely Available from IEEE

Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology