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Magnetics, IEEE Transactions on

Issue 3 • Date May 2002

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Displaying Results 1 - 19 of 19
  • Integration of magneto-optical garnet films by metal-organic chemical vapor deposition

    Publication Year: 2002 , Page(s): 1564 - 1567
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    This paper presents a novel technique for integrating yttrium iron garnets, namely Ce:YIG, onto semiconductor platforms using metal-organic chemical vapor deposition (MOCVD). Large amounts of cerium (Ce) could be incorporated into the garnet structure because of the nonequilibrium nature of the technique. The method can alloy up to 54% Ce, thereby increasing the refractive index and enhancing the Faraday rotation of the YIG films. Faraday rotations as high as 0.4°/μm at 1.3 μm were achieved in MOCVD-grown garnets, exceeding the rotations of bismuth-doped YIG films (0.15°/μm at 1.3 μm) grown by liquid-phase epitaxy. The easy axis of magnetization is within the plane of the films. When the garnet films were sputtered onto (100) magnesia (MgO) buffer layers, their hysteresis loops indicated that they were isotropic View full abstract»

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  • Contact-free moving-magnet type of micropositioner with optimized specification

    Publication Year: 2002 , Page(s): 1539 - 1548
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB) |  | HTML iconHTML  

    In this paper, we introduce a contact-free moving-magnet type of positioner that uses magnetic levitation to eliminate friction, the major limiting factor to high resolution on the micromanufacturing level. The promising magnetic structure consists of permanent magnets mounted on the stage and air-core solenoids, with little uncertainty, fixed on the stator. Since magnetically levitated systems are inherently unstable, the design concept focuses on stability. Combining the above elements with the repulsive force property, we suggest a novel six degrees-of-freedom Maglev positioner stabilized with minimum sensory feedback in space and have formulated the dynamic equation of the system by the linear perturbation technique. The chief design parameters are optimized to maximize the stable boundary. We present test results to verify the dynamic characteristics View full abstract»

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  • Multigrid methods for the three-dimensional simulation of nonlinear magnetomechanical systems

    Publication Year: 2002 , Page(s): 1497 - 1511
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (569 KB) |  | HTML iconHTML  

    We present a recently developed multigrid calculation scheme for coupled magnetomechanical systems. The scheme allows the efficient calculation of three-dimensional (3-D) dynamic rigid motions as well as deformations of nonmagnetic and ferromagnetic materials in a magnetic field. Thereby, the 3-D mechanical problem is discretized with nodal elements and the 3-D magnetic problem with edge elements. Both finite element meshes may be chosen independently and thus can be separately adapted to the physical requirements of the mechanical and magnetic fields. Fast multigrid solution techniques can solve large scaled 3-D problems within very short CPU times. Three examples demonstrate the efficiency of the developed scheme View full abstract»

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  • Comprehensive model of magnetization curve, hysteresis loops, and losses in any direction in grain-oriented Fe-Si

    Publication Year: 2002 , Page(s): 1467 - 1476
    Cited by:  Papers (13)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    We report an investigation and theoretical assessment of the DC magnetic properties of high-permeability grain-oriented (GO) Fe-Si laminations under variously directed applied fields. We verified that normal magnetization curves, hysteresis loops, and energy losses depend on the field direction according to the sample geometry. This is explainable in terms of specific 180° and 90° domain wall processes and magnetization rotations. We present a novel phenomenological theory of the magnetization curves and hysteresis losses in GO laminations, excited along a generic direction; the theory is based on the single crystal approximation and pre-emptive knowledge of the magnetic behavior of the material along the rolling (RD) and the transverse (TD) directions. This approach is consistent with the general structure of Neel's phase theory, with the additional consideration of hysteresis and losses. Epstein and cross-stacked sheet testing methods are the two base measuring configurations; all the other testing geometries (single sheet, disk, square) are expected to display intermediate behavior. The devised model provides, through a direct procedure, thorough and accurate prediction of magnetization curves and quasi-static losses in these two basic cases. Its application to the other geometries is equally possible, with only a limited amount of supplementary information View full abstract»

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  • Calculation of magnetic field strength and electromagnetic ponderomotive force of separators

    Publication Year: 2002 , Page(s): 1528 - 1533
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (301 KB) |  | HTML iconHTML  

    This paper presents a new type of conformal mapping function of two unequal segments onto equal ones. It develops analytic expressions for calculation of the magnetic field strength and electromagnetic ponderomotive force. Finally, it compares theoretical values with experimental data View full abstract»

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  • Magnetic properties of CoSm thin films with Cr80V20 and Cr as underlayers

    Publication Year: 2002 , Page(s): 1568 - 1574
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (294 KB) |  | HTML iconHTML  

    We investigated the static and time-dependent magnetic properties of thin CoSm films (6-14 nm) on CrV underlayers. We measured remanent coercivities of up to 4.5 kOe and viscosity coefficients as low as 8%/decade for 14-nn films with remanent moment thickness product of 0.49 memu/cm2. We compared magnetic hardness, interactions, viscosity, and anisotropy with similar films grown on Cr underlayers, and found that CrV constitutes a better underlayer for CoSm thin film media, most probably because of improved epitaxy at the interface and a more favorable interface, microstructure, and topography View full abstract»

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  • How to characterize soft magnetic materials by measuring magnetic flux density in a rotating field apparatus

    Publication Year: 2002 , Page(s): 1477 - 1480
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB) |  | HTML iconHTML  

    This paper deals with the characterization of the magnetic permeability of soft magnetic materials under a rotating magnetic field. The paper reviews the principle of the rotating-flux-density device used for measurement of flux density, then describes the mathematical method used to calculate permeability from the measurements. The method combines direct and inverse solutions and is based on a functional minimization sequence. An example demonstrates the validity of the method. Finally, the paper discusses the uniqueness of the solution and its sensitivity View full abstract»

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  • Separation of small nonferrous particles using an inclined drum eddy-current separator with permanent magnets

    Publication Year: 2002 , Page(s): 1534 - 1538
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    This paper presents a method for separating small metallic nonferrous particles from two-component nonferrous mixtures using, a new type of dynamic eddy-current separator with permanent magnets. The so-called inclined drum eddy-current separator (IDECS) consists of an inclined vertical rotary drum covered with permanent magnets, alternately N-S and S-N oriented, directly fixed on the axis of an electric engine. The particles to be separated are brought into the field on an oblique trajectory, hit the drum, and are deflected in the variable field under electrodynamic and mechanical interactions. The strongly conducting and poorly conducting particles assume different trajectories depending on their electrical conductivities, which lead to their separation. The paper presents the results of grade and recovery of wastes consisting of small particles (under 5 mm) derived from Cu-Pb and Cu-Al mixtures. The advantages of IDECS are that its efficiency is close to that of the usual dynamic eddy-current separator and its equipment cost is lower. A disadvantage is that the intermediate product must be passed again through a separation process View full abstract»

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  • Coil impedance due to a sphere of arbitrary radial conductivity and permeability profiles

    Publication Year: 2002 , Page(s): 1452 - 1460
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (426 KB) |  | HTML iconHTML  

    This paper presents analytical expressions for coil impedance due to a spherical workpiece consisting of concentric spherical shells. The expressions are used to simulate the nondestructive inspection of a sphere having arbitrary radial conductivity and magnetic permeability profiles by a circular coil of rectangular cross section. The simulation replaces continuous profiles with piecewise constant profiles. The paper compares the results to published experimental measurements and the results of other analytical solutions View full abstract»

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  • Comparison of various methods for calculating the AC resistance of inductors

    Publication Year: 2002 , Page(s): 1512 - 1518
    Cited by:  Papers (40)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    The paper reviews several expressions for high-frequency winding resistance of inductors proposed by several authors and compares the theoretical predictions calculated from these expressions with experimental results. It identifies the expressions that yield the most accurate prediction of the winding high-frequency resistance. The comparison shows that the method proposed by Dowell (1966) accurately predicts the AC resistance if the winding contains less than three layers. The methods proposed by several other authors accurately predict the high-frequency resistance only in certain frequency ranges. In addition, these expressions yield inaccurate results for the inductor quality factor. One expression, however, accurately predicts both the high-frequency winding resistance and the quality factor of inductors over a wide frequency range from the DC to the first resonant frequency. The paper concludes with a simple and accurate circuit model describing the frequency behavior of inductors View full abstract»

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  • Multiobjective optimization method based on a genetic algorithm for switched reluctance motor design

    Publication Year: 2002 , Page(s): 1524 - 1527
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    In this paper, a novel multiobjective optimization method based on a genetic-fuzzy algorithm (GFA) is proposed. The new GFA method is used for optimal design of a switched reluctance motor (SRM) with two objective functions: high efficiency and low torque ripple. The results of the optimal design for an 8/6, four-phase, 4 kW, 250 V, 1500 r.p.m. SRM show improvement in both efficiency and torque ripple of the motor View full abstract»

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  • Evaluation of test procedures for determining servo compatibility of heads and media in magnetic disk drives

    Publication Year: 2002 , Page(s): 1575 - 1592
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    We evaluate a testing specification proposed by the National Storage Industry Consortium's (NSIC) Extremely High Density Recording (EHDR) group for evaluating head and media compatibility for servo performance in magnetic disk drives. These tests use average amplitude and average noise profile measurements across isolated tracks to predict the shape, linearity, noise, and long-term stability of position error signal (PES) patterns. We compare the predictions from these tests to measurements from null and amplitude PES patterns written on a spin-stand. Results show average PES-profile prediction errors of 1%-2% track width and noise level prediction within a factor of 2. We present data from tests for long-term stability of the magnetoresistive (MR) read element after repeated write cycles by the inductive write head. In the set of heads we tested, the MR head's center and effective width changed only slightly. Although we evaluated the NSIC specification for MR read elements, the specification should be equally valid for other read head types also, as long as the PES patterns are similar View full abstract»

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  • Generation of remote homogeneous magnetic fields

    Publication Year: 2002 , Page(s): 1553 - 1563
    Cited by:  Papers (17)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (366 KB) |  | HTML iconHTML  

    This paper presents a magnetic efficiency model for comparing efficiencies of various magnets for magnetic resonance imaging. It demonstrates that monohedral magnets, magnets with sources on one side, can generate remote saddle points in the field profile relatively efficiently. These magnets may be modeled by a minimum of two magnetic dipoles. The paper examines the field profile and magnetic dipole efficiency for the two-dipole model in detail, and develops some fundamental properties of homogeneous magnetic fields View full abstract»

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  • Adaptive compensation for position error signal nonlinearity

    Publication Year: 2002 , Page(s): 1593 - 1602
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    The magnetoresistive (MR) magnetic head is a poor positioning transducer for a disk file's servo control system because its positioning response is nonlinear with radial displacement. This paper shows how the MR head's poor positioning properties are alleviated by a self-adjusting adaptive algorithm that allows a disk file to linearize its own servo position error signal (PES). The adaptive linearizer uses a nonlinear state estimator whose nonlinearity adjusts to match the nonlinearity of the PES. As the match between the two nonlinearities adaptively improves, the state estimator gives increasingly accurate estimates of the true actuator position View full abstract»

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  • Evaluation of inverse algorithms in the analysis of magnetic flux leakage data

    Publication Year: 2002 , Page(s): 1481 - 1488
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB)  

    We evaluate the use of linear and nonlinear inverse algorithms (maximum entropy method, low resolution electromagnetic tomography, L 1 and L2 norm methods) in the analysis of magnetic flux leakage (MFL) measurements commonly used for the detection of flaws and irregularities in gas and oil pipelines. We employed MFL data from a pipe with well-defined artificial surface breaking flaws at the internal and external wall. Except for the low-resolution electromagnetic tomography, all algorithms show, on average, similar accuracy in the flaw extent estimation. Maximum entropy and the L1 norm have a tendency to yield better results for smaller flaws, while the L2 norm performs slightly better for larger flaws. The errors of the flaw location estimation are comparable for the maximum entropy and the L2 norm algorithm. The L1 norm performs worse for those flaws situated on the internal pipe wall. Linear methods (L2 norm) are easier to implement and require less computation time than nonlinear methods (maximum entropy method, L1 norm). In conclusion, inverse algorithms potentially provide a powerful means for the detection and characterization of flaws in MFL data View full abstract»

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  • Nonlinear three-dimensional magnetic field computations using Lagrange finite-element functions and algebraic multigrid

    Publication Year: 2002 , Page(s): 1489 - 1496
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    The paper proposes an efficient solution strategy for nonlinear three-dimensional (3-D) magnetic field problems. The spatial discretization of Maxwell's equations uses Lagrange finite-element functions. The paper shows that this discretization is appropriate for the problem class. The nonlinear equation is linearized by the standard fixed-point scheme. The arising sequence of symmetric positive definite matrices is solved by a preconditioned conjugate gradient method, preconditioned by an algebraic multigrid technique. Because of the relatively high setup time of algebraic multigrid, the preconditioner is kept constant as long as possible in order to minimize the overall CPU time. A practical control mechanism keeps the condition number of the overall preconditioned system as small as possible and reduces the total computational costs in terms of CPU time. Numerical studies involving the TEAM 20 and the TEAM 27 problem demonstrate the efficiency of the proposed technique. For comparison, the standard incomplete Cholesky preconditioner is used View full abstract»

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  • Residual and compressive stress effects on tensor magnetization

    Publication Year: 2002 , Page(s): 1461 - 1466
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    We measured tensor hysteresis loops for a 25.4 mm steel cube with compressive stress applied orthogonal to the field, and studied the repeatability of compressive stress effects in terms of the maximum magnetization and differential susceptibility amplitudes. The nonrepeatability of results and anomalous low stress behavior can be attributed to stress hysteresis, specifically to residual stress View full abstract»

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  • Permanent-magnet assemblies for magnetic. Resonance imaging devices for various purposes

    Publication Year: 2002 , Page(s): 1549 - 1552
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    A high-performance magnet generating a homogeneous field contributes significantly to the quality of magnetic resonance imaging (MRI), and permanent-magnet assemblies, which can be specially configured for the particular whole body, pediatric, or orthopedic use, unlike superconducting and resistive magnets, help to ensure homogeneity. The paper surveys the suitability of tunnel-like, ordinary, and elliptic-cylinder-like configurations of permanent magnets in these uses View full abstract»

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  • Correct voltage distribution for axisymmetric sinusoidal modeling of induction heating with prescribed current, voltage, or power

    Publication Year: 2002 , Page(s): 1519 - 1523
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    We consider the problem of determining the voltage in coil rings, which arise as an axisymmetric approximation of a single connected induction coil during modeling of induction heating. Assuming axisymmetric electromagnetic fields with sinusoidal time dependence, we compute the voltages from the condition that the total current must be equal in each ring. Depending on whether total current, total voltage, or total power is prescribed, different linear systems of complex equations represent the ring voltages. In two sets of numerical simulations, varying the number of coil rings, we compare results using the correct voltage distribution to the corresponding results using the simple homogeneous voltage distribution View full abstract»

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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