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Magnetics, IEEE Transactions on

Issue 2 • Date Mar 2000

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Displaying Results 1 - 15 of 15
  • One-sided fluxes in planar, cylindrical, and spherical magnetized structures

    Page(s): 440 - 451
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    In planar structures, magnetization patterns exist that have the surprising property that all the external fringing field of flux emerges from one side of the structure, with precisely none appearing on the other side. In the last 25 years, this fact has led to a number of useful applications. More recently, the same concept has been found to hold for both cylindrical and spherical hollow structures, where all the fringing flux emerges either inside or outside the structure, with precisely none appearing on the other side. Again, this has led to a number of important practical applications. While many of the concepts have been published previously, this paper contains, for the first time, a uniform mathematical analysis of these one-sided flux configurations. Additionally, the paper reviews the principal applications of one-sided flux structures View full abstract»

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  • Contribution of the crystalline phase Fe100-xSix to the temperature dependence of magnetic properties of FINEMET-type alloys

    Page(s): 508 - 512
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    The temperature dependence of the hysteresis loop, saturation magnetization, and saturation magnetostriction of rapidly quenched ribbons of the compositions Fe100-xSix (x=12.1, 13.8, 20.0) and of FINEMET-type material with compositions Fe73.6 Cu1Nb3Si13.5B9 Fe73.5Cu1Nb3Si16.5B6 were measured between room temperature and 400°C. This paper analyzes the temperature dependence of the saturation magnetostriction and the saturation magnetization of the FINEMET ribbons after various heat treatments, assuming a superposition of the properties of the nanocrystalline Fe-Si and of the remaining amorphous phase. The behavior of the coercivity of Fe-Si prepared by rapid solidification follows roughly that of the (absolute value) of the magnetostriction. The Curie temperature of the remaining amorphous phase is enhanced View full abstract»

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  • Patterned media write designs

    Page(s): 521 - 527
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    Recording design alternatives are analyzed for 100 1 Gbit/in2 vertical and horizontal patterned media, written at 1 Gbit/s with one and two pole heads. Bit write fields, disturb fields, and switching speeds are calculated as part of a system analysis of the theoretical potential of patterned media to address possible physics limits for conventional “featureless” continuous film media (these include thermal decay, nonlinear transition shift and transition noise, and high writer pole Ms requirements near the limit of known materials). The patterned media “bits” are assumed oriented vertically or horizontally by crystalline anisotropy, and smaller than 100 nm to allow single-domain, 1/2 ns switching. MsHc V/kT>500, implying thermal stability including media demagnetization and write head remanent fields, are nearly an order of magnitude areal density extensibility beyond 100 Gbit/in2 with present-day head/media magnetic requirements View full abstract»

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  • Combatting partial erasure and transition jitter in magnetic recording

    Page(s): 532 - 536
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    Practical recording channels deviate significantly from the oft-used model based on linearity and additive Gaussian noise. Among the well-known anomalies are partial erasure and transition jitter. In this paper, we first describe a precompensation technique to combat the partial erasure effect. It utilizes the unique property of the maximum transition run (MTR) code wherein all dibits are isolated. The idea is to increase the spacing between the two transitions that make up each dibit. This tends to mitigate the nonlinear amplitude reduction associated with partial erasure. Next, we consider a recording channel that is linear but subject to transition jitter. We modify the hyperplane-based detector known as 3D-110 by introducing data-dependent threshold terms. The overall complexity of the detector is small, yet this modification provides almost 2 dB of improvement relative to the original 3D-110 structure and the extended partial response maximum likelihood (EPRML) method tuned to additive Gaussian noise View full abstract»

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  • Vector potential integral formulation for eddy-current probe response to cracks

    Page(s): 461 - 469
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A boundary integral vector potential formulation has been developed to evaluate eddy-current interactions with three-dimensional finite cracks in conductors. The approach is compared with an electric field integral equation method also used for solving crack problems in eddy-current nondestructive evaluation. An important advantage of the vector potential integral formulation is that the kernel has a weak singularity, but a drawback is that two unknown functions must be found on the crack surface. One of these functions, the current dipole density, represents the effect of the crack in terms of an induced source, and the other function is a solution of the two-dimensional Laplace equation. By contrast, the source density alone is needed for a complete solution of the electric field integral equation. In order to determine the surface Laplacian for finite cracks of arbitrary shape, a general numerical solution utilizing the boundary element technique is introduced. Numerical predictions of the eddy-current probe response to a crack give good agreement with experimental measurements, supporting the validity of the formulation View full abstract»

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  • Macroscopic models of magnetization

    Page(s): 418 - 428
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    Four magnetization models, now considered as classical, are presented: the Stoner-Wolhfarth model, the Jiles-Atherton model, the Globus model, and the Preisach model. The paper describes the methods each model uses to simulate the magnetization mechanisms, reversible and irreversible processes, major and minor loops, and anhysteretic behavior. Improvements and changes are proposed to the Stoner-Wolhfarth and Globus models. The necessary simplifying assumptions define the limits of applicability of the models. The paper concludes with a table of the main characteristics of each model to help a potential user to make a suitable choice View full abstract»

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  • Submillisecond spin-stand measurements of thermal decay in magnetic recordings

    Page(s): 528 - 531
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    The time dependence of magnetic recordings is determined on a spin stand by observing the amplitude of different spectral components of the readback signal from about 200 μs to 11 s after writing. Measurement times shorter than one revolution period of the disk are obtained by placing separate write and read heads on the same track. An increased decay rate in the fundamental signal amplitude is observed at higher linear recording densities. The decay deviates from ln (t) at short times. Comparison of the decay rates of the spectral components of different density recordings indicates transition broadening over time View full abstract»

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  • Magnetic circuit model for the mutually coupled switched-reluctance machine

    Page(s): 500 - 507
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    The mutually coupled switched-reluctance motor (SRM) appears to have several performance advantages over other motor technologies. The existence of strong coupling between phases, however, makes the analysis of this machine quite complicated. Preliminary design of this machine can be greatly accelerated by the ability to evaluate potential motor geometries quickly. This paper introduces a general magnetic circuit model of the mutually coupled SRM that adapts to any geometry, unlike existing geometry-dependent approaches (such as finite elements), which are numerically intensive and require excessive computation time. The model uniquely implements the magneto-motive force (mmf) sources necessary to accommodate complex flux paths through the machine and includes the effects of magnetic saturation. The results are compared to those of a finite element solver to demonstrate the performance of this method as a first-step to evaluating candidate designs View full abstract»

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  • Nonlinear analysis of the three-phase transformer considering the anisotropy with voltage source

    Page(s): 491 - 499
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    In this paper, the Newton-Raphson method, using two-directional (anisotropic) material properties, is applied to the analysis of a three-phase transformer. A new two-dimensional (2-D) model that reflects three-dimensional manufacturing effects, such as air-gap and overlapped stacking, is proposed. These effects cannot be dealt with by conventional 2-D methods. In addition, the new method obtains the current waveform phase difference with respect to the voltage source waveform. The analysis is performed by a finite-element method in which a voltage source is included, and its validity is confirmed experimentally View full abstract»

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  • Energy-based hysteresis model for magnetostrictive transducers

    Page(s): 429 - 439
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    This paper addresses the modeling of hysteresis in magnetostrictive transducers in the context of control applications that require an accurate characterization of the relation between input currents and strains output by the transducer. This relation typically exhibits significant nonlinearities and hysteresis because of inherent properties of magnetostrictive materials. The characterization considered here is based on the Jiles-Atherton mean field model for ferromagnetic hysteresis in combination with a quadratic moment rotation model for magnetostriction. As demonstrated by comparison with experimental data, the magnetization model very adequately quantifies both major and minor loops under various operating conditions. The combined model can then be used to accurately characterize output strains at moderate drive levels. The advantages of this model lie in the small number (six) of required parameters and its flexibility under a variety of operating conditions View full abstract»

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  • Energy calculation of a permanent magnet system by surface and flux integrals (the flux-mmf method)

    Page(s): 470 - 475
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    Formulas are derived for the total magnetic energy of a system with no currents, linear soft magnetic materials, and linear permanent magnets that satisfy a zero curl condition involving their magnetization vector (zero equivalent volume current density). This class of magnets includes common parallel and radially magnetized NdFeB and ferrite magnets above the knee in their demagnetization curves. The formulas express the energy as a constant plus either an integral over the magnet surface of the magnetic vector potential or an integral through the magnet of the magnetic flux. The formulas provide theoretical foundation for the flux-magnetomotive force (mmf) method for calculating cogging torque of permanent magnet motors View full abstract»

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  • Homogeneous magnet design using linear programming

    Page(s): 476 - 483
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    We introduce a technique for designing homogeneous magnets using linear programming, We first show that minimum-power homogeneous magnet design can be cast as a linear programming problem. We also show that the method is applicable to minimum conductor mass superconducting magnet design. The method has several advantages over existing techniques including: it allows complete flexibility in arbitrary geometric constraints on both the coil locations and the shape of the homogeneous volume; it guarantees a globally optimal solution; and it offers rapid computation speed (about 30 s). Three resistive magnet design examples and one shielded superconducting magnet design are presented to illustrate the flexibility of the method View full abstract»

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  • Magnetic properties, microstructures, and corrosion resistance of high-saturation FeMoN and FeRhN films for recording heads

    Page(s): 513 - 520
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    We have investigated high-saturation FeMoN and FeRhN films, deposited by radio frequency-diode reactive sputtering on alumina-TiC substrates, for inductive head applications. A minimum coercivity of ~1.2 Oe is obtained in (Fe97.8Mo2.2)N films at a N 2/Ar flow ratio of ~6.2%. A minimum coercivity of ~1.6 Oe is obtained in (Fe96.9Rh3.1)N films at a N2/Ar flow ratio of ~4.6%. The films mainly consist of α-Fe phase and γ'-Fe4N phase; The magnetic properties of these films are stable under easy axis field annealing up to 350°C. Addition of Rh or Mo to FeN has resulted in a significant improvement in corrosion resistance over that of FeN. The localized corrosion resistance of FeRhN and FeMoN can be comparable to that of Permalloy. In contrast, their intrinsic corrosion resistance is inferior to that of Permalloy, but it can be adjusted and controlled by pH level View full abstract»

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  • Design procedure for permanent magnet assemblies with uniform magnetic fields for MRI devices

    Page(s): 484 - 490
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    This paper shows that for magnetic resonance imaging (MRI) permanent magnet assemblies with the pronounced pole pieces, the investigation of magnetic field generated by one pole piece is a way to obtain an interrelation between pole piece diameter, magnet assembly air-gap length, and first and second shim dimensions. The investigation makes it possible to design optimum magnet assemblies View full abstract»

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  • Multidomain analytical-numerical solution for a rotating magnetic field with a finite-length conducting cylinder

    Page(s): 452 - 460
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    This paper treats the rotating magnetic field produced by a cylindrical sheet of temporally and azimuthally periodic axial electric current with a finite-length, electrically conducting cylinder surrounded by an electrical insulator inside the current sheet. As the frequency is increased, the magnetic field produced by the induced current in the cylinder cancels progressively more of the current-sheet magnetic field in the interior of the cylinder. This paper presents results for several different frequencies and for several different length-to-diameter ratios for the cylinder. It compares the results at the midplane of a long cylinder to the analytical solution for an infinitely long cylinder. It also compares results for a high frequency to the predictions from the first two terms in an asymptotic expansion for high frequency 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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Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology