IEEE Transactions on Magnetics

Issue 4 • July 1991

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Displaying Results 1 - 25 of 28
  • A new theory of recording media noise

    Publication Year: 1991, Page(s):3519 - 3531
    Cited by:  Papers (31)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1206 KB)

    Previous investigations of the noise in particulate or grainy recording media have considered statistical variations in the processes by which the particles become magnetized. The theory of noise presented includes also statistical variations in the packing density of the particles. An extremely simple analysis shows that, when both of these phenomena are included properly, the noise power of reco... View full abstract»

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  • Dynamics of domains and walls in soft magnetic films

    Publication Year: 1991, Page(s):3532 - 3538
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (683 KB)

    General equations are derived to describe the simultaneous nonuniform planar rotations of the magnetization vector and displacements of curved domain walls and their junctions in soft magnetic films. These equations take into account effects of exchange stiffness, magnetic anisotropy, external and either long- or short-range demagnetizing fields, wall energy, and dissipation. The case of a matched... View full abstract»

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  • Magnetostatic energy calculations

    Publication Year: 1991, Page(s):3539 - 3547
    Cited by:  Papers (45)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1017 KB)

    Magnetostatic self-energy can in principle be calculated by evaluating a certain sixfold integral, though this is not practical even for very simple cases. It is pointed out that some analytic transformation of this integral can facilitate computations, especially with an appropriate choice of Ritz models. A review of these is followed by a review of some of the methods that have been used for num... View full abstract»

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  • A resistor network theory of the giant magnetoresistance in magnetic superlattices

    Publication Year: 1991, Page(s):3548 - 3552
    Cited by:  Papers (83)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (487 KB)

    An explanation of the giant magnetoresistance effect observed in some magnetic superlattices is given in terms of an equivalent network of resistors. The model leads to a simple analytic formula that relates the magnetoresistance to the spin-dependent electron mean-free paths and thickness of the magnetic and nonmagnetic layers in the superlattice. The formula is used to study the giant magnetores... View full abstract»

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  • Magnetization structures in thin-film recording media

    Publication Year: 1991, Page(s):3553 - 3562
    Cited by:  Papers (21)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1184 KB)

    A computer simulation study of magnetization configurations in planar isotropic thin-film recording media and their transient behavior during magnetization reversal is presented. Magnetization structures formed during magnetization reversal are characterized for various medium parameters. It is found that a reversed region nucleates by formation of a magnetization vortex. Multiple vortex formation... View full abstract»

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  • Models of the longitudinal digital magnetic recording process in thin films

    Publication Year: 1991, Page(s):3563 - 3569
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (598 KB)

    A review of the various mathematical models of the longitudinal recording process in thin-film recording media is given. One of the main focuses of the review is on the arctangent theories of recording, and these are discussed in terms of both their successes and their failures. More recent work shows an increasing trend towards determining the nature of the recorded distributions directly from th... View full abstract»

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  • Spin-glass behavior in a fine particle system

    Publication Year: 1991, Page(s):3570 - 3578
    Cited by:  Papers (159)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (729 KB)

    A study of the magnetic behavior characteristic of a spin-glass, which has been examined for systems of ultrafine particles, is reported. The results obtained support the suggestion of E. P. Wohlfarth (1977) that spin-glass effects could arise from the clustering of impurity spins in the host material into ferromagnetic rich clusters. All the results are explained on the basis of the Neel superpar... View full abstract»

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  • Magnetization process in Permalloy multilayer films

    Publication Year: 1991, Page(s):3579 - 3587
    Cited by:  Papers (12)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (3072 KB)

    The magnetization process in positively coupled double and multilayered systems of Permalloy separated by carbon layers has been investigated. Domain patterns appearing in this process have been observed by both Lorentz electron microscopy and high-resolution Kerr effect. The patterns display a microstructure different from that observed in the single films, e.g., twin walls with crossing points, ... View full abstract»

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  • The exchange-spring magnet: a new material principle for permanent magnets

    Publication Year: 1991, Page(s):3588 - 3560
    Cited by:  Papers (1647)  |  Patents (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1635 KB)

    It is proposed that permanent magnets can be made of composite materials consisting of two suitably dispersed ferromagnetic and mutually exchange-coupled phases, one of which is hard magnetic in order to provide a high coercive field, while the other may be soft magnetic, just providing a high saturation J/sub s/, and should envelop the hard phase regions in order to prevent their corrosion. A gen... View full abstract»

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  • Demagnetizing factors for cylinders

    Publication Year: 1991, Page(s):3601 - 3619
    Cited by:  Papers (283)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1799 KB)

    Fluxmetric (ballistic) and magnetometric demagnetizing factors N/sub f/ and N/sub m/ for cylinders as functions of susceptibility chi and the ratio gamma of length to diameter have been evaluated. Using a one-dimensional model when gamma >or=10, N/sub f/ was calculated for -1 View full abstract»

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  • FMR and EXAFS modeling of heat-treated Fe-rich and Co-rich TM-M thin films

    Publication Year: 1991, Page(s):3620 - 3639
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1744 KB)

    Ion-beam sputter-deposited alloy films of Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ and Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ were examined for their magnetic and structural properties. Films were characterized by ferromagnetic resonance, vibrating sample magnetometry, and extended X-ray absorption fine structure (EXAFS) analysis. Using atomic parameters deduced from EXAFS modeling and fitting procedu... View full abstract»

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  • Recent development of thin film materials for magnetic heads

    Publication Year: 1991, Page(s):3640 - 3647
    Cited by:  Papers (36)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (730 KB)

    Recent developments of soft magnetic film materials in the past decade are reviewed. Approximately 20 kinds of alloy systems with high saturation induction of more than 10 kG have been reported in the last decade, although there were only three conventional head materials: Mn-Zn ferrite, Permalloy, and Sendust. A particular focus of the review is nanocrystalline films and multilayer films. Also re... View full abstract»

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  • Giant magnetooptic rotations: the role of orbital polarization and explicit correlation effects

    Publication Year: 1991, Page(s):3648 - 3654
    Cited by:  Papers (28)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (659 KB)

    An ab initio itinerant-electron calculation for a class of cerium and uranium compounds was performed over the full frequency range studied experimentally. The band structure is obtained from a self-consistent spin-polarized full-potential linearized muffin-tin orbital calculation with a true interstitial. It was found that, for the compounds that display giant Kerr rotations, such a conventional ... View full abstract»

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  • Fine particle high gradient magnetic entrapment

    Publication Year: 1991, Page(s):3655 - 3677
    Cited by:  Papers (44)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (2045 KB)

    The entrapment of fine colloidal paramagnetic (and diamagnetic) particles at magnetic capture centers in the colloid is reviewed. The effect of thermal diffusion on the entrapment from a static colloid is examined in the 1-D and 2-D cases. The latter case allows prediction of captured volumes of colloidal particles. The interparticle effects due to the Helmholtz double-layer electrical interaction... View full abstract»

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  • Anisotropy pinning of domain walls in a soft amorphous magnetic material

    Publication Year: 1991, Page(s):3678 - 3689
    Cited by:  Papers (45)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (2307 KB)

    Ribbons were annealed in the demagnetized state with one wall along the ribbon middle. This wall becomes pinned during the heat treatment. Reentrant reversal occurs when reverse domains are nucleated at the ribbon edge with a threshold field larger than the demagnetizing field; this wall does not annihilate when it meets the pinned wall but leaves a line of reverse domains stabilized by ripple in ... View full abstract»

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  • Investigation of coercive squareness in TbFeCo films

    Publication Year: 1991, Page(s):3690 - 3696
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1012 KB)

    TbFeCo is one of the most promising magnetooptical recording media because it shows a high uniaxial anisotropy and a fairly good Kerr effect, and its composition can be tailored to achieve a large room temperature coercivity. A basic study was carried out to determine the factors affecting the mechanisms of magnetization reversal and the regularity of domain growth at room temperature in TbFeCo fi... View full abstract»

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  • Existence of magnetization-dependent Preisach models

    Publication Year: 1991, Page(s):3697 - 3699
    Cited by:  Papers (30)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (239 KB)

    I. D. Mayergoyz (1986) has shown that the necessary and sufficient conditions for a hysteretic process can be described by a classical Preisach model are that it possesses the wiping-out property and the congruency property. Magnetization-dependent Preisach models also have the wiping-out property but do not possess the congruency property. The necessary and sufficient conditions for a process to ... View full abstract»

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  • Effect of orienting fields on agglomeration in dilute dispersions of magnetic fine particles

    Publication Year: 1991, Page(s):3700 - 3703
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (403 KB)

    Static light scattering was used to investigate dilute dispersions of fine gamma -Fe/sub 2/O/sub 3/ magnetic particles. The particles were acicular and on average 0.39 mu m long and 0.056 mu m in diameter. They were dispersed in organic solvents at concentrations of approximately 10/sup -4/ vol%, corresponding to an average interparticle separation of 9 mu m. Computer programs using a coupled dipo... View full abstract»

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  • Nonlinear eddy current effects in ferromagnetic materials in the presence of DC magnetic fields

    Publication Year: 1991, Page(s):3704 - 3709
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (474 KB)

    Eddy current effects in nonlinear ferromagnetic materials in the presence of a supplementary DC magnetic field are analyzed. The analysis is for a one-dimensional configuration, a semi-infinite plate magnetized homogeneously in a direction parallel to its surface. The nonlinear magnetization characteristic of the ferromagnetic plate material is assumed to be of a step-function form. Solutions of t... View full abstract»

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  • Transient eddy current distribution in the shield of the passively compensated compulsator-air-core machines

    Publication Year: 1991, Page(s):3710 - 3720
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (872 KB)

    The eddy current distribution in the shield of an air-core passively compensated pulsed alternator (compulsator) is discussed. The action of the shield reduces the inductance of the armature winding considerably, thus enabling it to deliver high-power pulse to low-impedance loads. By virtue of its function, the shield is stressed mechanically as well as thermally. An analytical solution of the 2-D... View full abstract»

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  • Quantitative evaluation of coupling factor and its application

    Publication Year: 1991, Page(s):3721 - 3730
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (771 KB)

    A numerical analysis of the coupling factor k, its applicable examples, and new formulas are described. A formula of 'reflectivity gamma ' of the magnetic flux, i.e., the ratio of the induced flux to the incident flux in a secondary coil whose winding is closed or in a metal conductor, has been derived in the process of theorizing k. In its straightforward application to nondestructive inspection,... View full abstract»

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  • Electromechanical railgun model

    Publication Year: 1991, Page(s):3731 - 3734
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (299 KB)

    The electromechanical aspects of railgun motion are modeled analytically. A Lagrangian formulation is used to obtain the force and circuit equations, which are then solved for energy conservation and resistive flux decay. The resulting integral equation is solved for the barrel length as a measure of the launcher size and cost. The solution for a lossy railgun with multiple conductors (augmented c... View full abstract»

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  • Feasibility study of an electromagnetic thruster for ship propulsion

    Publication Year: 1991, Page(s):3735 - 3742
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (662 KB)

    A comprehensive computational feasibility study is presented for an outer-type electromagnetic thruster intended for ship propulsion. A thruster previously presented in the literature is modeled in a way to keep computer power needed in reasonable limits despite wide coverage of the efficiency estimates. For this purpose a two-dimensional approach is adopted. It is also shown how to generalize the... View full abstract»

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  • The dependence of direct overwrite characteristics on the magnetic properties of DC magnetron sputtered films

    Publication Year: 1991, Page(s):3743 - 3750
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (613 KB)

    The magnetization of rare-earth transition metal films was varied by changing the compensation and the Curie temperatures independently. The coercivity was varied by depositing films with different thicknesses and with an underlayer of silicon nitride. The direct overwrite characteristics investigated include the minimum pulsewidth for erasing and writing a certain size domain, the pulsewidth marg... View full abstract»

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  • An analysis of the magnetic field of a ring head with a highly permeable underlayer

    Publication Year: 1991, Page(s):3751 - 3755
    Cited by:  Papers (11)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (422 KB)

    An idealized mathematical model of the magnetic field due to a ring head with a highly permeable underlayer is solved using Fourier analysis. Accurate Fourier coefficients are derived for a range of gap dimensions. The leading term of the resulting exact series is shown to be equivalent to a previously published approximation, but it is demonstrated that this term alone is not normally sufficient ... 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