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Magnetics, IEEE Transactions on

Issue 4 • Date July 1986

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Displaying Results 1 - 12 of 12
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Magnetic bubble logic component library

    Page(s): 217 - 238
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    A comprehensive library of magnetic bubble logic components has been established, with emphasis on standardization in terms of dimensions and I/O to facilitate VLSI chip composition. These components were designed in a current-access perforated-sheet configuration and fabricated on magnetic garnet wafers supporting 2-µm bubbles. The operating margin for each component was studied individually on 8-µm period devices at 1 MHZ by using a high-speed magneto-optical sampling-camera system. The bubble-to-bubble interaction force was found to be very reliable in producing successful logic operation with a 12-percent bias-field margin for the XOR/AND gate equal to 80 percent of the bubble-propagation margin and about 60 percent of the free-bubble bias-field margin. The experimental results show 10.8, 10.7, 10.2, 10, 10.6, 8.5, 12, 8.5, 15, and 9.5-percent bias-field margins for the SWITCH, AND/OR, COMPARATOR, SEARCH, LATCH, BIT-PAIR SEPARATOR, MERGER, CROSSOVER, ANNIHILATOR, and SPLITTER gates, respectively. An 8.5-percent overlapped bias margin has been obtained for all of the logic components. Transient pictures taken with a small incremented delay revealed that the bubble motion in perforated-sheet logic devices is uniform both in the velocity excursion and shape distortion. The behavior of various components at different values of the bias field and drive current is all qualitatively interpretable on the basis of experimental observations. The feasibility of these logic components is successfully demonstrated. View full abstract»

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  • Ion-implanted and permalloy hybrid magnetic bubble memory devices

    Page(s): 239 - 246
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    Hybrid bubble memory devices have been proposed and operated with the memory density of 4 Mbit/cm2. In the hybrid bubble memory devices, minor loops are composed of ion-implanted tracks with 4-µm period, and major lines and functional parts including block-replicate and swap gates are composed of Permalloy tracks with a longer period of 12 µm. Passive junctions between ion-implanted and Permalloy tracks have been developed, introducing the tapered ion-implantation technique. Improving the characteristics of the functional parts composed of Permalloy tracks, the hybrid bubble memory devices with block-replicate and swap gates have been operated, and the feasibility of the devices has been confirmed. In addition, the possibility of higher memory density has been shown. View full abstract»

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  • DC modulation noise in thin metallic media and its application for head efficiency measurements

    Page(s): 247 - 252
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    A model for one type of modulation noise in thin-film metallic disks is presented based on experimental noise power spectra. It is observed that fluctuations in head-to-disk spacing produce noise proportional to the slope of the hysteresis curve. Experiments on a disk with distinctive surface texture illustrate that spacing variations due to surface texture may indeed be the dominant mechanism in this modulation noise. The data may also be analyzed using a mechanism of coercivity fluctuations. This noise may adversely affect data recording, since it occurs when the magnetization is changing most rapidly. The findings about the noise characteristics give rise to experimental techniques for measuring head efficiency and medium coercivity. View full abstract»

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  • Performance analysis of partial response systems for nonreturn-to-zero recording

    Page(s): 253 - 258
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    An analysis is presented of the performance of partial response (PR) systems of types PR(1, 0, 0, . . . , 0, -1) and PR(1, 0, 0, . . . , 0, 1) for nonreturn-to-zero recording. The error probability is obtained as a function of the signal-to-noise ratio (SNR) at the reading point, the phase margin, the linear density, and the roll-off factor of a Nyquist equalizing waveform. Then as a numerical example a performance comparison of the PR systems is made by obtaining the relation between the phase margin and the SNR required to achieve the prescribed error probability. View full abstract»

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  • Analytical investigation of eddy currents in nonlinear ferromagnetic media for weak magnetic fields

    Page(s): 259 - 271
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    Electromagnetic field diffusion into a nonlinear ferromagnetic conducting half-space is analytically investigated for weak magnetic fields. For these fields a "nth power" approximation for magnetization curves is used. The exact analytical solutions to the non-linear partial differential equations of electromagnetic field theory are found for circular polarization of incident waves. The case of noncircular polarization is treated as a perturbation of circular polarization. Linear equations for perturbations are then derived and their analytical solutions are found. The analytical theory is illustrated by the computational results for surface impedances and third harmonics of electromagnetic fields. View full abstract»

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  • Domain models of eddy current loss due to normal magnetization in slightly misoriented

    Page(s): 272 - 281
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    In Goss-oriented SiFe laminations, regions exist with a significant normal magnetization component arising from dip misorientation of the crystallites. It has recently been suggested by Imamura and co-workers that this normal magnetization can make a major contributionP_{perp}to the eddy current losses incurred during cyclic magnetization along the texture axis.P_{perp}is calculated for three distinct domain models of the magnetization process in laminar crystallites with modest dip misorientation. Contrary to the Imamura work,P_{perp}is found to be practically negligible for a simple slab domain structure without closure domains. This is because the normal demagnetizing field restricts normal induction to the neighborhood of the domain walls and ensures that its volume average is practically zero. In a second model monotonic reversal of normal magnetization in closure domain structures is also shown to give rise to rather low normal lossP_{perp}. A third model concerns how closure domains may interact with the major boundaries between slab domains and be swept along with them. Quite substantial lossesP_{perp}are predicted if all closure domains in a zone extending a distance rather greater than the sheet thickness either side of the major domain wall are displaced in this way. However, even this mechanism can explain only a small part of the marked increase in eddy loss with dip misorientation reported, and it is concluded that normal flux is probably not primarily responsible. View full abstract»

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  • An eddy-current model for three-dimensional inversion

    Page(s): 282 - 291
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    A model is presented for the inversion of eddy-current data to be used for the detection of flaws. This model is based on rigorous electromagnetic theory and uses a multifrequency approach to make it truly three-dimensional. The resulting integral equations are discretized and solved using least squares techniques. The numerical problems involved in this algorithm are discussed, and a solution as well as examples of reconstructions of computer-generated flaws are presented. View full abstract»

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  • The use of null field integral equations in magnetic-field problems

    Page(s): 292 - 298
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    The objective of this paper is to discuss the use of the null field integral equations in the solution of eddy current magnetic field problems. Their usage is approached through a development of the "classical" boundary integral equation technique as applied to irregularly shaped two-dimensional objects. Two immediate advantages are discussed, the first being the circumvention of singularities in the integrands. The second is the ability to improve the conditioning of the determination matrix by appropriate choice of null field points. The technique is tested on an irregularly shaped ellipsoid and results compared to those obtained from perturbation theory. View full abstract»

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  • A fluxgate magnetometer with a metallic glass core

    Page(s): 299 - 300
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    A square-wave excited pulse-height fluxgate circuit is described, using a metallic glass core fluxgate and a minimum amount of active components. High reliability and linearity have been achieved. View full abstract»

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  • [Back cover]

    Page(s): 0
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    Freely Available from IEEE
  • Propagation of reversible magnetization changes along ferromagnetic amorphous ribbons

    Page(s): 301 - 305
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    Local reversible magnetization changes are produced in a region of a long ferromagnetic amorphous ribbon, and their amplitude decay versus the distance from this region is measured. The amplitude decay is analyzed as a function of the reversible permeability on as-cast and annealed ribbons of various widths and thickness at different points of the hysteresis loop. The results are discussed on the basis of the theoretical flux conduction of a magnetically homogeneous cylindrical sample. The results agree with the theoretical model of the magnetic flux conduction on homogeneous materials only for low values of the reversible permeability. The larger deviation, occurring at high values of permeability, are ascribed to both the sample shape and the nonhomogeneous magnetic structure due to magnetic domains. 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