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Magnetics, IEEE Transactions on

Issue 5 • Date Sep 1993

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Displaying Results 1 - 17 of 17
  • Formulas for the force and torque of axial couplings

    Page(s): 2295 - 2301
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Closed-form expressions are presented for computing the force and torque that is transmitted by synchronous axial couplings. These expressions enable rapid parametric studies of coupling performance relative to the selection of magnet material, dimensions, and spacings. They are also useful for testing three-dimensional numerically based field algorithms. The derived expressions are tested here using data taken from a ceramic coupling View full abstract»

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  • Linear AC magnetic circuit theory

    Page(s): 2207 - 2212
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    A theory is presented for linear, AC magnetic circuits. The theory develops real and imaginary reluctance terms, which are used in the same manner as real and imaginary impedance terms in linear, AC electrical circuit theory. The reluctance terms can be manipulated through coil-coupled resistances and capacitances. The theory is applied to a parallel magnetic-circuit configuration to show the limits of applicability for the particular materials from which the circuit is constructed View full abstract»

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  • Characteristics of a thin film microtransformer with circular spiral coils

    Page(s): 2232 - 2237
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    A thin-film 3.14-mm×3.88-mm microtransformer has been fabricated, using photolithography technology, to support high-frequency switching regulators. The microtransformer is composed of sputtered amorphous magnetic layers, electroplated copper windings with 20-μm width, and insulator layers. The coupling factor between the primary and secondary windings of the microtransformer is 0.97 for f=3 MHz. An input-output voltage ratio of 0.95 at 15 MHz is obtained at no-load. Observation of the domain images under high-frequency excitation indicates that the magnetic anisotropy of the microtransformer films is induced by rotating magnetic field annealing so as to increase the output voltage View full abstract»

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  • Media requirements and recording physics for high density magnetic recording

    Page(s): 2185 - 2201
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    Relevant aspects concerning the ultimate achievable recording densities for particulate as well as for thin-film media are discussed. This review covers the entire range starting from micromagnetics of individual single domain particles, moving on to their magnetic behavior in a particle assembly under particular consideration of the structure being actually obtained in the process of manufacturing recording media, and finally embarking on an outline of recording physics. These considerations are not only carried out for longitudinally and perpendicularly oriented recording media but also for media having an arbitrary orientation of the easy axis of magnetization. All aspects are discussed and illustrated for the first commercially available thin-film medium on a flexible substrate, which is the metal evaporated tape, i.e., the obliquely deposited Co-Ni-O layer for the Hi8 video system View full abstract»

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  • On plane magnetic fields in saturable materials

    Page(s): 2213 - 2220
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    The equations governing two-dimensional flux and potential fields in nonlinear soft magnetic materials can be converted into a pair of linear conditions by means of a Legendre transformation. On this basis and for certain classes of constitutive equations, exact solutions are found that describe configurations such as plane multipole fields and fields near corners and edges. In case of perfectly saturable materials the formation of perfectly permeable domains is observed, and their shapes are determined View full abstract»

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  • Digital recording theory for thick media

    Page(s): 2286 - 2288
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    The familiar theories of digital recording (such as that of Williams and Comstock) which apply to thin films are extended to apply to thick media. The result is a theory which is able to predict variations of transition widths through the depths of the media, making it more widely applicable View full abstract»

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  • Safety and protection of 8 T NbTi gyrotron magnet in persistent mode

    Page(s): 2238 - 2243
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    To achieve high mechanical stability of a superconducting winding, numerical stress-strain analyses of the winding structure and appropriate stress-strain analyses of the winding structure and appropriate epoxy-impregnation technology were applied. To improve further winding mechanical stability, an initially round 1-mm-diameter varnish-insulated conductor was flattened to rack-track cross section (1.25 mm×0.75 mm for the inner section, 1.31 mm×0.65 mm for the rest of the magnet). The stainless steel road (1 mm diameter) of the bandage was flattened in the same way (up to 1.14 mm×0.77 mm). The danger of creating a hot spot region was limited by radial magnet sectioning and section shunting by low ohmic shunts. The superconducting switch was protected by a pair of antiparallel silicon diodes mounted between magnet flanges in parallel to it. The high threshold voltages of the diodes at 4.2 K allow system run-up with relatively high speed without any limitation on the sign of the magnet field polarity View full abstract»

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  • Anisotropic stress in window-plated Permalloy thin films

    Page(s): 2266 - 2272
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    Measurements of stress have been made in window-plated strips of Permalloy with different aspect ratios and the results have been related to finite-element simulations. It is found that the in-plane stresses in the window-plated strips are similar to those expected in strips fabricated from a sheet film with an initial biaxial stress state. The effect of annealing the strips is to increase the difference between the two principle in-plane stresses. The implications of this stress state for the magnetic anisotropy of the strips is discussed View full abstract»

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  • Magnetic circuits classification

    Page(s): 2221 - 2227
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    A classification of magnetic circuits is proposed. It is based on the circuit's working geometry, its components (magnets, pole pieces, yokes), and the nature of its source (dipole, quadrupole, multipole). Examples of conventional devices and recent developments are given for the different classes considered View full abstract»

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  • Calculation of an electromagnetic field in a three-phase induction pump with a compensating winding

    Page(s): 2289 - 2294
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    A three-phase inductor which generates a magnetic traveling field is often used in induction liquid metal pumps. Due to the finite length of the inductor an alternating magnetic field component occurs, which should be compensated. An analysis of the electromagnetic field of an induction pump with a rectangularly shaped transport channel and a flat three-phase inductor possessing a compensating winding is presented. It is based on a computational model which takes into account the finite length and width of an inductor winding and nonuniform velocity distribution along the liquid metal depth. The calculations of magnetic flux density distributions in liquid zinc were carried out for an induction pump with and without compensating winding View full abstract»

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  • Magnetostatic image theory for an arbitrary current loop in front of a permeable sphere

    Page(s): 2202 - 2206
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    Magnetostatic image theory recently introduced for the problem of a circular current loop in front of a permeable sphere centered on the axis of the loop is generalized to the case of an arbitrary current loop outside the sphere. The theory is derived by finding the image for a current element outside the sphere. As an application, the image for a straight line current is seen to result in a surface current in the form of a circular disk. The present theory is also seen to reproduce that for the circular loop as a special case. The analytic form of the image current is simple enough to be applicable in small-scale computation for problems involving a permeable sphere and stationary current View full abstract»

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  • Magnetic structure design method

    Page(s): 2228 - 2231
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    The method described provides a simple procedure for the design of structures intended to generate a magnetic field that follows a specific variation law in an air gap. The emphasis is on design rules derived from well known theorems such as the superimposition principle, the easy axis rotation theorem, and the image theorem. An example is given for a linear displacement sensor application. Magnetic structures for producing trapezoidal or triangular magnetic induction profiles consist of simple yoked and yokeless configurations. An experimental device has been designed and built with the help of analytical and numerical calculations View full abstract»

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  • Reciprocity principles for magnetoresistive heads

    Page(s): 2279 - 2285
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    A generalized reciprocity principle for magnetoresistive (MR) heads is derived. The results apply primarily to the linear (small signal) reproduce performance of any MR head type (shielded or unshielded, single or multiple active MR elements) of arbitrary three-dimensional geometry. Reciprocity principles provide a powerful technique for calculating the intrinsic sensitivity function that is characteristic of a given MR reproduce head, and which in principle contains all information regarding the linearized reproduce response of the MR head with respect to any record medium of arbitrary recorded magnetization. The computational work required to evaluate the sensitivity function via reciprocity is a small fraction of that which would be required by direct means View full abstract»

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  • Influence of the magnetic after-effect (MAE) on the frequency dependence of the complex initial susceptibility: a tutorial approach

    Page(s): 2273 - 2278
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    The theory of the complex initial susceptibility in the presence of a magnetic aftereffect (MAE) is treated, with special attention paid to the case of a MAE of the stretched exponential type. This case is of importance for the study of the initial complex susceptibility in complex correlated systems, which present an MAE of a nonsimple exponential nature View full abstract»

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  • An approach to recording on tilted media

    Page(s): 2258 - 2265
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    A simple model for recording on media with a tilted anisotropy axis is proposed. The model combines the slope theory (Williams and Comstock model) with vectorial aspects of the head fields, their corresponding gradients and the angular dependence of the switching fields of the medium. In the case of obliquely deposited metal evaporated tape, the model is shown to predict the experimental data correctly View full abstract»

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  • On the application of moment methods to electromagnetic nondestructive evaluation

    Page(s): 2244 - 2250
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    The application of moment methods (MMs) to eddy-current testing problems for nondestructive evaluation (NDE) is considered. A general formulation for the MM that can be used to analyze NDE problems is derived, and calculated results and experimental data obtained from eddy-current testing of an artificially made sample are presented. Good agreement between the calculated results and the experimental data confirms the validity of the method and shows that the MM can be used as an alternative to the finite-element method (FEM) and the boundary-element method (BEM) in NDE View full abstract»

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  • Magnetoresistive sensors with rapidly solidified Permalloy fibers

    Page(s): 2251 - 2257
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    The microstructure and properties of Permalloy fibers were studied. Both transverse and longitudinal extraordinary magnetoresistive effects have a positive initial slope due to stress-related rotation of moments in the closure domains and to the coherent rotation of moments in the columns. Fiber response was also investigated as a function of the field direction and angle of incidence, fiber twisting and for strong transverse fields. The results are discussed in terms of the existing models, and a new model is proposed to explain the transerse effect. The structures and operating principles of single- and dual-fiber biased sensors based on the longitudinal effects are presented. Distortions due to overbiasing are accounted for by the pinning and expansion of large-area closure domains with moments tilted by the casting stress. The sensitivity-linearity range product is the same for several bias levels, and a family of sensors was obtained using the same fiber 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