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Magnetics, IEEE Transactions on

Issue 4 • Date Jul 1997

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Displaying Results 1 - 16 of 16
  • Subharmonic ferroresonance in an LCR circuit with hysteresis

    Publication Year: 1997 , Page(s): 2495 - 2500
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    We use the Preisach model of magnetic hysteresis to model the inductance in a series LCR circuit. By introducing a hysteresis parameter into the Preisach functions used, we are able to continuously vary the width of the hysteresis loop and thereby investigate the effects of magnetic hysteresis on the circuit's behavior. In particular, it is shown that the stability region of a period-3 subharmonic ferroresonant solution can increase significantly as the hysteresis losses are reduced. The bifurcations leading to the appearance and disappearance of this subharmonic solution are examined. Also, strong numerical evidence is provided for the unsuitability of single-valued M-H curves in the analysis of ferroresonant phenomena View full abstract»

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  • Fabrication and characterization of a concentric cylindrical microtransformer

    Publication Year: 1997 , Page(s): 2501 - 2503
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    This paper describes the use of a nonphotolithographic technique-microcontact printing-to fabricate a concentric cylindrical microtransformer having an outer diameter of ~350 μm. For frequencies of up to 20 kHz, this microtransformer has a high coupling coefficient (>0.9). At higher frequencies, properties of the ferromagnetic material used in the construction of the microtransformer limit performance View full abstract»

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  • Data storage and retrieval using perpendicular media and magnetoresistive read transducer

    Publication Year: 1997 , Page(s): 2538 - 2542
    Cited by:  Papers (4)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    We have investigated magnetic recording on multilayer perpendicular media using a conventional peak detect channel and a commercial magnetoresistive recording head. A finite impulse response filter was used to equalize the impulse response from perpendicular media into a unipolar pulse. Equalized pulses had a PW50 of 174 nm and a D50 of 131 kfei. Without write precompensation, a linear density of 204 kbits per inch (kbpi) with a 3.3 ns error window margin and a data transfer rate of 75 Mbit/s was measured with an error rate of 4×10-7. The signal waveform was stable and had good up-down amplitude symmetry View full abstract»

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  • Distortion effects on servo position error transfer function

    Publication Year: 1997 , Page(s): 2569 - 2572
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    Two kinds of nonlinear distortion of hard-disk-drive position error signal (PES) transfer function are examined and modeled. The first distortion is the saturation of the PES due to narrow read width. The second distortion is the on-track dead band at the center of the transfer function due to wide erase band. Several formulas are developed to describe the relationships between the distortion effects and the design parameters: read width, track spacing, and erase width. These distortions are highly undesirable for the track following sectored servo system. However, they are predictable and avoidable if certain conditions are satisfied. The geometrical analysis of the distortion phenomenon is presented here View full abstract»

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  • Analytical solutions to eddy-current testing problems for a layered medium with varying properties

    Publication Year: 1997 , Page(s): 2473 - 2477
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    A one-parameter family of analytical solutions is found for the case where a single-turn coil is located above a two-layer conducting medium. The conductivity σ and the relative magnetic permeability μ of the upper conducting layer are constants, while for the lower conducting half-space, these are of the form σ(z)=Azb and μ(z)=Bza, where A and B are constants and a+b=-2 or a+b=0. The change in impedance is computed, and the results of numerical simulation are presented View full abstract»

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  • Crossfeed problems in read-while-write tape heads

    Publication Year: 1997 , Page(s): 2531 - 2537
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    Three-dimensional finite element models have been utilized to simulate the crossfeed problems in read-while-write (RWW) tape heads, and the results have been compared with experimental measurements. The most significant contributors, such as shield structure, intershield spacing, and reproductive mode, have been identified. A new thin-film inductive/dual-magnetoresistive tape head design was found to reduce the crossfeed by about a factor of 30, compared with the conventional shared-pole design, which is the most favored approach for achieving simultaneous operation of the READ head and WRITE head View full abstract»

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  • Analysis of track-edge noise in thin-film recording media

    Publication Year: 1997 , Page(s): 2509 - 2512
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    Track-edge noise has been analyzed to clarify track-edge noise mechanisms. Edge noise arises from two different regions: the bit edge where the magnetization direction is opposite to the previously dc-erased direction and the magnetic transition edge. The edge noise at low density is mainly due to the magnetic distribution at the bit edge. The transition edge noise increases with increasing recording density, and it becomes dominant at high-recording density for an oriented medium. On the other hand, the transition edge noise is almost constant with increasing recording density for an isotropic medium View full abstract»

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  • Crossover condition in the coherent rotation model and the Preisach-type models

    Publication Year: 1997 , Page(s): 2573 - 2579
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The crossover of the hysteresis branches in the classical coherent rotation model is analyzed. The analysis is extended when the truncated Stoner-Wohlfarth astroid is used. The physical explanation of the crossover occurrence is given. More accurate expressions of the anisotropy free energy density are required to better describe the behavior of the system when the angle between the easy axis and the magnetic moment of the particle is near 90°. A simple approximate formula for the hysteresis loop branches, which are in good agreement with those obtained when the discussed corrections are made, is given. The effect of the use of the Stoner-Wohlfarth astroid in the calculus of the equilibrium state in some vector Preisach-type models is analyzed View full abstract»

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  • Analytical and numerical solution of the eddy-current problem in spherical coordinates based on the second-order vector potential formulation

    Publication Year: 1997 , Page(s): 2461 - 2472
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The three-dimensional (3-D) eddy-current problem, described in spherical coordinates, is studied both analytically and numerically. Since the vector field equation is not separable in the spherical coordinate system, the second-order vector potential (SOVP) formulation is used to treat the problem by reducing it to the solution of the scalar field equation. While the analytical solution is expressed in terms of known orthogonal expansions, the numerical solution utilizes the finite difference method. Examples of engineering applications are provided, concerning computation of eddy-current distribution in a conducting sphere by a filamentary excitation of arbitrary shape View full abstract»

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  • Analytic study of the effects of shield recession on the replay characteristics of an idealized MR sensor

    Publication Year: 1997 , Page(s): 2543 - 2551
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    A previously published two-dimensional conformal mapping solution for a shielded magnetoresistive (MR) sensor is used to explore the effect that recessing the shields has on replay from a vertically oriented medium in the presence of a soft magnetic underlayer. The horizontal and vertical head-field components, spectral response function, linear dibit shift, and roll-off curve of each of two heads, where the sensor tip and the shield faces are coplanar, are compared with those of the same heads with recessed shields. By recessing the shields, the solution may be applied to the case of an unshielded MR sensor View full abstract»

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  • Simple electromagnetic detection of variations in properties of metal surfaces

    Publication Year: 1997 , Page(s): 2492 - 2494
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB)  

    Recently, a significant improvement in the sensitivity of the nonuniform AC field measurement technique for the detection of cracks was reported. In this paper, the results of the application of the improved technique in the detection of heat-effected zones and ground welds are presented and briefly discussed. In such applications, the use of a long probe is essential View full abstract»

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  • Interaction fields evaluation in fine particle systems

    Publication Year: 1997 , Page(s): 2504 - 2508
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    A computer simulation model for estimation of the interaction fields in fine particle systems has been developed. The method uses the experimental δMa(H) plot, constructed from the Fourier description of the initial magnetization curve and the hysteresis loop, and the δM(H) plot, obtained from the remanence curves. The dependencies of the interaction fields on the external magnetic field have been obtained from the experimental data for a sample of a Ba-ferrite fine powder View full abstract»

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  • Environmental effects on the streaming mode performance of metal evaporated and metal particle tapes

    Publication Year: 1997 , Page(s): 2513 - 2530
    Cited by:  Papers (15)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    A commercial Hi-8 video cassette recorder was instrumented to measure friction force between the rotary heads and tape, rms head output, and signal dropouts to sub μs duration. Streaming (play) mode experiments using metal evaporated (ME) and metal particle (MP) tapes were performed at design tension under equilibrium and nonequilibrium conditions inside of an environmental chamber at various temperature and specific humidity (SH=ratio of the weights of water vapor to dry air in the mixture). Interface stability and recording performance at a 0.6 μm recording wavelength were measured to bit level resolution using a dropout counter and changes in rms head output were correlated to changes in head-to-tape spacing using the Wallace equation. ME tape performed best at moderate SH (from 0.009 to 0.013) in the operating temperature range of 15.6 to 32.2°C, whereas MP tape performed best at low temperature. At a given temperature, higher SH increased normal and friction forces and decreased head-to-tape spacing due to spontaneous water meniscus formation between contacting and noncontacting asperities on the head, tape, and debris particle surfaces. Dropout frequency and interface stability were sensitive to both SH and temperature. Humidity dependence was governed by the relative size difference between wear debris particles and spontaneously formed water menisci. Competing mechanisms of increased lubricant mobility and spontaneously formed water menisci of smaller radii of curvature at higher temperature governed temperature dependence. A model based on capillary condensation of water vapor onto surfaces in a sliding contact is developed to explain experimental data. An expression for meniscus force consisting of both Laplace and surface tension contributions is developed for nanometer size contact spots and wear debris particles. The model predicts that meniscus force will increase and head-to-tape spacing will decrease with increasing SH which was observed experimentally. Four lubrication regimes are defined for wear debris particles passing through the contact interface. Both SH and extent of deformation of a particle determine whether menisci will form around the particle, and presence or absence of associated meniscus forces explains trends in dropout frequency data. The model allows determination of meniscus height from which minimum values of Kelvin radius and relative humidity (RH) in the contact interface can be calculated. Proximity and intimate contact of the surfaces increases RH and SH in the contact interface over that maintained in the environmental chamber to near their saturation values View full abstract»

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  • Model order reduction for optimal bounding ellipsoid channel models

    Publication Year: 1997 , Page(s): 2552 - 2568
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    This paper presents a new algorithm for performing model order reduction for Volterra series channel models of high-density digital magnetic recording channels. We employ a set-membership approach to the problem in which a set of consistent modeling solutions bounded by an optimal ellipsoid is first developed for the channel. We then present a new algorithm for finding the minimum number of coefficients in the Volterra series expansion which preserves the accuracy, in a least-squares sense, of the reduced order model in comparison with the original model View full abstract»

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  • Nonlinear calculation of three-dimensional static magnetic fields

    Publication Year: 1997 , Page(s): 2486 - 2491
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    We present here the principle and structure of a method to calculate the three-dimensional (3-D) static magnetic fields which have already permitted us to study hybrid magnets for magnetic resonance imaging and ion confinement. Field sources can be issued from resistive or superconducting coils, permanent magnets, and other magnetic bodies such as soft iron. It can be extended to very low-frequency fields calculation as long as eddy current effects do not intervene. We call this method CALMAG3D View full abstract»

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  • Prediction and use of impedance matrices for eddy-current problems

    Publication Year: 1997 , Page(s): 2478 - 2485
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Inclusion of both skin and proximity effects in the prediction of impedance matrices in eddy-current problems significantly complicates the prediction of the impedance matrix. In this paper, a technique employing a boundary element method is used to predict these impedance matrices using an additional constant vector potential which is added to the interior of every conductor. This constant vector potential is slightly altered for an axisymmetric problem and allows for the easy prediction of induced voltage in an eddy-current conductor. Perhaps the greatest contribution offered by this paper is in the interpretation of these matrices and in particular, with the negative components comprising the resistance matrix. The phasor diagrams, both for voltage and current as well as magnetic fields, are employed to aid in better understanding the information delivered within the impedance matrix. The explanations are directed specifically toward a three-coil axisymmetric problem. The technique is tested against the measured voltage in a three-phase current fed system 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