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Magnetics, IEEE Transactions on

Issue 3 • Date May 1979

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Displaying Results 1 - 19 of 19
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Magnetic bubble device scaling and density limits

    Page(s): 1009 - 1016
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    Scaling of magnetic bubble devices to smaller bubble sizes and higher density is considered. Drive field requirements, materials requirements, fabrication requirements, current requirements, and detector signal-to-noise ratio are all calculated as a function of bubble size and related to practical limits imposed by bubble materials, fabrication techniques, and electromigration limits. It is concluded that "conventional" bubble devices using Permalloy bars can be made practical with 1-μm bubble domains (storage densitysim6 times 10^{6}bits/cm2). Although it may be possible to extend these Permalloy bar devices to even smaller bubbles, it seems more likely that other bubble devices such as contiguous disk devices or bubble lattice devices will in fact be used for densities greater than 6 × 106bits/cm2. View full abstract»

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  • Some characteristics of ion-implanted bubble chips

    Page(s): 1016 - 1020
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    The relations between the position of charged walls and the bubble motion around propagation circuits are discussed. Long walls which extend between adjacent propagation loops are revealed by the Bitter technique. The examination of the domain structure in the implanted layer shows the existence of a magnetic gradient which is a function of the distance from the propagation circuits. The switching of magnetization in particular directions of the in-plane field is reported and correlated with the bubble movement. An additional easy axis is observed along the circuits due to shape anisotropy. Propagation margins are very similar to those obtained with permalloy circuits. Fabrication technology as well as design of 16 μm period circuits is discussed. Nucleation and transfer have been achieved with currents in the range of 50 mA to 200 mA. Phase margins of about a quarter of a period are found, and bias field margins fall between 10 and 15 Oe. View full abstract»

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  • A simple method for computing wall twist in high-Q bubble materials

    Page(s): 1021 - 1026
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    First-order perturbation of the one-dimensional structure for the wall surrounding a bubble domain, lead to a set of linear differential equations, which should determine the wall twist for any magnetic material with a large quality factor Q provided the wall is stationary. A first-order solution of these equations is given in terms of two linear integrals whose numerical evaluation is much simpler than the evaluation of wall structure by minimizing numerically the wall energy, as has been done so far. Examples are given for the wall twist thus computed for several film thicknesses, which should give an idea of what the twist is when Q is large enough. For medium Q, however, the accuracy of the method turns out to be inadequate. View full abstract»

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  • Analysis of gap-tolerant bubble circuits

    Page(s): 1026 - 1031
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    A technique is presented for the analysis of bubble propagating circuits using a numerical model previously discussed. Various gap-tolerant bubble circuits are analyzed using this model and potential well profiles are plotted. The analysis of these circuits clearly shows the advantages of the asymmetrical structures over the symmetrical ones. By postulating the various failure modes, bias margins are computed which are in good agreement with experimental results. View full abstract»

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  • On the theory of bubble domain motion in propagation circuits

    Page(s): 1031 - 1046
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    The stability conditions for a bubble domain in the fields of magnetostatic traps are analyzed. For this purpose the quasi-stationary equations of bubble motion are derived which take into account field nonuniformity across the bubble diameter. The contribution of the Permalloy overlay is considered qualitatively. The conditions of static and dynamic stability of trapped bubbles are studied and the stability role in the operating margin development is analyzed. View full abstract»

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  • Record head saturation in AC bias recording

    Page(s): 1046 - 1049
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    The head core saturation problem in ac bias audio recording is analyzed. An approximate expression, which should be satisfied in order to avoid head saturation, is obtained in terms of head core saturation flux density Bm, gap length g, tape coercivity Hc, and tape coating thickness δ. Experimental verification is obtained by using various values of Bm,g,Hc, and δ. View full abstract»

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  • Effect of bitshift distribution on error rate in magnetic recording

    Page(s): 1050 - 1053
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    A formalism is presented which relates the intrinsic error rate of a digital recording channel to measurable channel parameters: interpulse interactions and signal-to-noise ratio. Experimental data is provided to support the theoretical model. Implementation of the formalism allows clear identification of recording channel limitations and provides a method for determining the most reliable use of the channel. View full abstract»

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  • External bit field analyses

    Page(s): 1054 - 1059
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    Three-dimensional external bit fields emanating from single and multiple magnetic transitions with a finite track width have been calculated. The magnetic field interferences between tracks have been also simulated. The results show that the fields have a large component in the track width direction near the transition edges. This contributes to field extension in the neighboring track direction. The amount of extension decreases with bit density increase. The results of our calculations are backed up by Lorentz microscopy observation of films in which bit fields are transcribed. View full abstract»

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  • Narrow track magnetic head fabricated by ion-etching method

    Page(s): 1060 - 1064
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    Manufacturing narrow track magnetic heads is difficult as track widths become very narrow. A new flying-head manufacturing method is established by applying ion-etching. Optimum conditions for ion-etching of the ferrite material were determined. More than 10 μm ion-etched depth and even less than 5 μm track width were obtained. Through experimental and theoretical evaluation, it is proven that ion-etched heads have equivalent or better read/write characteristics than mechanically manufactured heads. View full abstract»

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  • Magnetostriction and stress-induced playback loss in magnetic tapes

    Page(s): 1065 - 1067
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    A direct correspondence between magnetic tape playback level, stress-induced remanence loss, and magnetostrictive properties of corresponding magnetic oxides has been observed. From these results the amount of playback loss was estimated by stressing a short segment of tape, by measuring magnetostriction in compacts of magnetic pigments or by an analysis of the Fe2+and Co2+content if the state of the cobalt within each particle is known. View full abstract»

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  • Influence of reduction temperature on coercivities, coercivity factors and rheological properties of γ-Fe2O3and silica coated γ-Fe2O3

    Page(s): 1068 - 1072
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    The transformation of α-FeOOH into γ-Fe2O3via Fe3O4is studied in order to determine the influence of the reduction temperature on the magnetic and rheological properties of the final product. The study was carried out both on pure and on silica coated α-FeOOH. It was found that the reduction temperature at which a maximum of coercivity is obtained, varies with particle size, and it is much higher for silica coated samples which also show higher coercivity at the optimum reduction temperature. Coercivity factors (CF percent) and Mr/Ms values are also dependent on particle size. It is shown that coating with silica enables the reduction to be carried out at higher temperatures without significant collapse of the acicular shape. View full abstract»

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  • Mechanical properties of barium hexaferrites

    Page(s): 1072 - 1074
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    The mechanical properties of typical isotropic barium ferrites have been determined. A statistical analysis has shown that fracture toughness is the best quality parameter. It changes with variation of production operation conditions. The fracture statistics follows the Weibull distribution. A relationship is found between the influence of the Fe2O3/BaO molar ratio on mechanical and magnetic properties. A maximum of mechanical and magnetic properties has been observed when the SiO2content in sintered ferrites is about 0.9 percent. View full abstract»

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  • Computational methods for solving static field and eddy current problems via Fredholm integral equations

    Page(s): 1075 - 1084
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    Two-dimensional static field problems can be solved by a method based on Fredholm integral equations (equations of the second kind). This has numerical advantages over the mote commonly used integral equation of the first kind. The method is applicable to both magnetostatic and electrostatic problems formulated in terms of either vector or scalar potentials. It has been extended to the solution of eddy current problems with sinusoidal driving functions. The application of the classical Fredholm equation has been extended to problems containing boundary conditions: 1) potential value, 2) normal derivative value, and 3) an interface condition, all in the same problem. The solutions to the Fredholm equations are single or double (dipole) layers of sources on the problem boundaries and interfaces. This method has been developed into computer codes which use piecewise quadratic approximations to the solutions to the integral equations. Exact integrations are used to replace the integral equations by a matrix equation. The solution to this matrix equation can then be used to directly calculate the field anywhere. View full abstract»

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  • Computer-aided design of air-gapped magnetic core inductors with minimum DC winding resistance

    Page(s): 1085 - 1096
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    The method of computer-aided design of air-gapped inductors operating with de bias current is described. An algorithm for the minimum de resistance of the winding for a desired value of the inductance is given. Simultaneously, this permits us to determine the optimal length of the air gap, to choose a suitable operating point on the normal magnetization curve and to calculate the minimum number of turns of the winding under given inductor operation conditions, i.e., the ac voltage value across the inductor and its frequency, and the value of the de bias current superimposed in the same winding. The method presented here uses the normal magnetization curve of the core material and the family of relative incremental permeability curves of this material. View full abstract»

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  • Applications of multiterminal representations to magnetic fields

    Page(s): 1096 - 1102
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    A graph-theoretic approach to the formulation of discrete models of magnetic field problems with special emphasis on the application of multiterminal representations is presented. The discrete model is obtained directly from the physics of the field, thus obviating the need for the usual intermediate analytical formulation (partial differential equation, energy functional, etc.). Further, the discrete models of large sparsely connected subregions (elements) may be obtained from the discrete model in terms of multiterminal representations. These models are then used to solve the entire field while providing both conceptual and computational advantages. View full abstract»

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  • Moments and force densities of the electrodynamic levitation system

    Page(s): 1102 - 1108
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    Theoretical predictions of the moments and the force density distributions on the superconducting magnet and on the conducting sheet guideway are given for the reference levitation system design proposed for the Canadian Maglev vehicle. The theoretical method is based on the Lorentz force,tilde{J} times tilde{B}and the solution follows from a combination of the dynamic circuit theory and the EM field theory already developed. Very good correlations are found with the moments measurements already published. The data from the predictions are important for vehicular mechanics analysis and for mechanical structural design of fastenings and bracings. View full abstract»

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  • [Back cover]

    Page(s): 0
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    Freely Available from IEEE

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