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Magnetics, IEEE Transactions on

Issue 2 • Date March 1983

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Displaying Results 1 - 14 of 14
  • [Front cover and table of contents]

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  • A new zero-ripple switching DC-to-DC converter and integrated magnetics

    Page(s): 57 - 75
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    A new switching dc-to-dc converter is synthesized which consist of the least number of storage elements (inductive and capacitive) and switches, and yet truly emulates the ideally desired dc-to-dc transformer having both input and output currents as pure dc quantities with no ripple. This result was facilitated by implementation of a new concept termed integrated magnetics, which leads in some special switching structures to the integration of otherwise independent and separate magnetic components (inductors and transformers) into a single magnetic circuit. View full abstract»

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  • New magnetic structures for switching converters

    Page(s): 75 - 83
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    In the past the majority of power processing applications have been centered around a very few standard switching converter topologies. Recently, a number of new converter topologies have been proposed in order to find the best possible electrical inter connection of power processing elements: switches, storage components, and transformers, that would yield the highest efficiency and best performance. However the equally important and complementary problem of their best magnetic interconnection has been completely overlooked. In some new converter structures, the nature of the switching process and existing waveforms allows integration of previously separate inductors and transformers into a single magnetic structure. Several such magnetic core structures are proposed and analyzed, which lead to further converter simplifications and performance improvements. View full abstract»

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  • On the noise power spectral density of particulate recording media

    Page(s): 84 - 89
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    The ac-noise power spectrum is investigated. Because of the interaction forces between the particles, the structure of the particulate layer has a dominant influence. This structure is quantified by means of the dc-noise power spectrum. Depending on the dispersion and coating technique the duster structure appears to vary. The ac-noise power is described by a mechanism of negative and positive interactions which occur simultaneously. Flux-closuring particles are near to each other at distances less than 0.1 μm, whereas magnetic strings appear to extend over tens of microns. View full abstract»

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  • The coercivity of multiple acicular particles

    Page(s): 90 - 94
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    It is known that the acicular particles comprising a tape coating often occur as groups of a very few single particles lying side by side, i.e., "multiple particles." The coercivity of such multiple particles was calculated and compared with that of the constituent single particles. In general it was found that the effect of multiplicity was to reduce the connecivity by up to 20 percent, which is small compared with the intrinsic variation of the coercivity within a given sample, which is of the order of 300 percent. View full abstract»

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  • Perpendicular stand-still recording in Co-Cr films

    Page(s): 94 - 104
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    Some features of perpendicular recording were investigated by means of stand-still recording experiments. For this purpose several radio frequency (RF)-sputtered Co-Cr layers of two different compositions were used as media while a Permalloy single pole (SP) head was used as a write transducer. A magnetoresistive transducer (MRT) was utilized to read the recorded pattern. Further, an analytical model was developed enabling the magnetization induced by the head field in the recording medium to be calculated. Both calculations and experimental results show a sharpening of the transition, due to the demagnetizing field. For a good approximation it is sufficient to consider only the vertical head field component and vertical magnetization in the recording medium. This is a consequence of the well-developed perpendicular anisotropy and negligible in-plane remanence of the Co-Cr layers. In addition the read-out signal is completely determined by the magnetic surface charges. The remanent magnetization in the recording medium and therefore the read-out amplitude is limited by demagnetization and consequently determined by the coercivity of the Co-Cr layer. The medium noise of a dc-erased medium indicates magnetic structures of much larger dimensions than the size of the individual crystallites. This noise appears to be dependent on the saturation magnetization of the Co-Cr medium. Activation of the single pole head by a homogeneous field results in a nonlinear behavior, caused by head saturation effects. This is supported by simple one-dimensional calculations of the head field. View full abstract»

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  • NiFeCo--An alternative to permalloy for bubble domain detection?

    Page(s): 104 - 110
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    The characteristics of bubble domain sensors fabricated from ternary NiFeCo films have been studied and compared with Permalloy film sensors. In 350 Å thick films, the ternary alloy exhibits a magnetoresistance ratio of 3.5 percent in contrast to 2.8 percent for Permalloy films prepared under similar conditions. Sensor sensitivity in functional bubble chips is correspondingly greater, while the sensor noise level is equal to-or lower than-that obtained with the Permalloy detector. Low coercivity and dispersion in NiFeCo films aid in producing an overall improvement in signal-to-noise ratio. The performance of NiFeCo sensors operating in 1-μm bubble ion-implanted contiguous-disk devices is described. View full abstract»

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  • Optimum design considerations for dual conductor bubble devices

    Page(s): 111 - 119
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    A design for dual conductor, current-access bubble devices with 8-μm periods has been optimized with a numerical calculation method for bubble motion in a propagating magnetic field, generated around hole patterns in conductor layers. Magnetic bias field distributions are calculated for an oval hole chain in the conductor layers. Bubble motion equations are obtained with analytical field distribution functions approximating the calculated field distributions. Minimum drive current density Jminfor normal bubble propagation is determined by a solution to the equations. The hole shape has been optimized by the minimization of the drive power Pmin, the product of Jminand conductor resistance, which is calculated from current distributions around the hole pattern. Optimum layer thickness have also been obtained for 8-μm period bubble devices. Both registration tolerance between the two conductor layers and bubble skew effects have been studied semiquantitatively on the basis of the equations of motion. The numerical calculation method developed here is found to be a highly effective means to optimize pattern design for smaller period devices. View full abstract»

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  • Three-dimensional eddy current problems using the T-Ω method and fredholm integral equations

    Page(s): 120 - 125
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    A technique is discussed for computing three-dimensional magnetic fields created by an oscillating source in a conducting medium. The technique's contribution lies in the manner in which the Fredholm integral technique is merged with a representation of the magnetic field as the sum of a vector and the gradient of a scalar (the T-Ω representation). The T-Ω representation is shown to conveniently realize the boundary conditions without introducing higher order derivative terms into the integral equations. The technique offers a powerful means of numerically calculating three-dimensional fields, necessitating only the discretization of interfacial surfaces. View full abstract»

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  • Characteristics of the capacitively loaded flux gate sensor

    Page(s): 126 - 130
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    Starting with a variational principle (through Lagrange's equation), a new and simpler form of the equations for reactively loaded flux gate elements has been developed. Apart from the simplicity of the derivation, the result offers the advantage that it is expressed in terms of easily measurable parameters. By capacitively loading the flux gate there may be obtained through parametric amplification sensitivity increases of two or more orders of magnitude without additional noise-producing components. In order to make optimal use of parameteric amplification, it is necessary to be able to predict the effect of component selection on operating point and on overall performance. Some unfortunate choices of components and operating points can lead to extreme sensitivity to component values, and other combinations can lead to oscillation. The theory of Fluoquet [1], as presented in Nayfeh and Mook [2], has been adapted to predict the stability of the solutions. We present plots showing the growth with time of currents and charge in typical unstable modes. Typical maps showing regions of stability and instability also are presented. The results agree with our laboratory observations. They provide a basis on which to make preferred design choices for practical instruments. View full abstract»

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  • Properties of amorphous alloy films mainly composed of Co--Nb

    Page(s): 131 - 135
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    Amorphous alloy films, mainly composed of Co-Nb, have been studied by radio frequency (RF) sputtering. These amorphous films having small magnetostriction show excellent soft magnetic properties after the magnetic annealing we have developed. One of them with the composition of (Co83.5Fe2)92/85.5Nb8was found to have very high saturation magnetizationB_{s} = 14300(gauss). The effects of additives such as Zr to the alloys have been investigated and amorphous films having high crystallization temperature as well as high saturation magnetization were successfully obtained. These amorphous films show fairly good wear and corrosion resistance as well as excellent thermal stability of the magnetic properties. View full abstract»

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  • [Back cover]

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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