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Magnetics, IEEE Transactions on

Issue 6 • Date November 1976

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Displaying Results 1 - 25 of 158
  • [Front cover and table of contents]

    Publication Year: 1976 , Page(s): 0
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    Freely Available from IEEE
  • Introduction to the proceedings of the first joint MMM-INTERMAG conference

    Publication Year: 1976 , Page(s): 607
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    Freely Available from IEEE
  • The crosstie memory

    Publication Year: 1976 , Page(s): 608 - 613
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    The crosstie memory stores information in magnetic domain walls in permalloy films about 350 Å thick. The domain walls are also used as shift register tracks. Serrated edges on narrow thin film permalloy strips are used to center a domain wall in each strip and to provide stable positions for crossties and Bloch lines. A magnetoresistance detector uses the same information bearing permalloy film as the magnetoresistive element. The entire crosstie memory can be fabricated on a silicon wafer or chip using conventional photolithographic procedures as are used in fabricating integrated circuits. Thus, a magnetic memory can be combined with semiconductor drivers, decoders, and sense amplifiers on the same chip. The memory is intended to serve as a block oriented random access memory (BORAM). Important background information such as static and dynamic stability conditions, Bloch line mobility, propagation and observation techniques are reviewed. Also, design goals and the role such device is expected to play in memory technology are presented. Anticipated performance includes a shift rate of 20 × 106bits/sec, a bit density greater than 1.5 × 105bits/cm2, an operating temperature range from -50 °C to 100 °C, nonvolatility, low cost, and low power consumption. View full abstract»

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  • 68 kbit capacity 16 µm-period magnetic bubble memory chip design with 2 µm minimum features

    Publication Year: 1976 , Page(s): 614 - 617
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    A bubble propagating structure that operates well on a 14 μm to 18 μm propagate period with a nominal 2 μm minimum feature size has been designed. The structure consists of only 1 discrete permalloy feature per circuit period. Sixty-eight kbit-capacity memory chips based on such structures have been designed, built, characterized, packaged and the packages have been characterized. The chip is organized as a set of minor (storage) loops with separate write and read major lines. The bubble manipulating functions, of which the replicate and transfer gates are the most critical, have also been designed with 2 μm minimum features. The design is adequate to provide a 14 Oe bias field margin range with drive fields of about 35 Oe, using a bubble garnet material with approximately 170 Oe free bubble collapse field. Sixty-eight kbit single loop shift register type chips designed using similar propagating structures, however, provide over 20 Oe bias field margin ranges with drive fields of about 35 Oe. View full abstract»

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  • Planar processing for magnetic bubble devices

    Publication Year: 1976 , Page(s): 618 - 621
    Cited by:  Papers (4)  |  Patents (3)
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    A two-mask level, conductor first thin film process is described for fabrication of magnetic bubble devices. The process permits a stepless permalloy level over a conductor that may be two to three times as thick as conventional processing The planar process is attained by anodizing a thick aluminum alloy film in all regions where no conductor is needed. The process described solves problems in conventional processing caused by thin conductor metalization and permalloy step coverage. Replication, nucleation, and annihilation devices made with this process promise superior performance. View full abstract»

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  • Bubble memory design and performance

    Publication Year: 1976 , Page(s): 622
    Cited by:  Papers (2)
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  • Superconductive computer technology

    Publication Year: 1976 , Page(s): 623
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  • Chip packing efficiency in bubble modules

    Publication Year: 1976 , Page(s): 624 - 628
    Cited by:  Papers (1)
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    A magnetic bubble mass memory system containing many chips may be configured in different ways. At one extreme, all the required chips are placed inside one drive coil set and one bias magnet. At the other extreme, each chip is placed in its own drive coil set and bias magnet, and the many single chip magnetic modules are then combined to form a mass memory system. This paper will compare these different approaches in terms of system volume and system power specifications. A generalized model will be described in order to compare these choices in configuration using a uniform set of packaging constraints. View full abstract»

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  • Multiple level storage organization for bubble memories

    Publication Year: 1976 , Page(s): 629
    Cited by:  Papers (1)
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  • A hybrid decoder bubble memory organization

    Publication Year: 1976 , Page(s): 630 - 632
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    A hybrid bubble organization is proposed which combines the advantages of both major-minor loop and decoder organizations while eliminating some of the complexity of the decoder organization. The organization consists of multiplexed decoder sections in which the selection of different blocks is performed in part by decoding and in part by a major-minor type time domain selection. The number of decoder steps can be reduced at the expense of a modest increase in access time. This organization allows the use of a low current retarding type decoder element, thus reducing the on-chip power consumption. Also, a number of decoder conductors can share the same driver, reducing the number of external chip connections. View full abstract»

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  • A fast access memory design using 3µm bubble 80K chip

    Publication Year: 1976 , Page(s): 633 - 635
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    A fast-access, non-volatile memory system using 3- μm bubble 80-kbit chips has been designed for an experimental model and evaluated from a systems viewpoint. The goal of this project is to investigate from both the side of technology and cost if the memories built with major-minor organized 3 μm bubble chips are acceptable in the commercial market. This paper describes the practical design of a bubble memory system, with a capacity of 8-Mbits and an average access time of approximately 1 ms at drive frequencies of up to 500 kHz, which involves memory system organization, redundancy design using chips with excess minor loops, packaging, electronic circuits scheme and other considerations. The results of the experiment and the system cost estimate based on this design are also described. View full abstract»

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  • Bubble memories for microcomputers and minicomputers

    Publication Year: 1976 , Page(s): 636 - 638
    Cited by:  Papers (2)
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    An analysis has been made of the utilization of 65,536 bit bubble memory chips in small memory hierarchies for microcomputers and minicomputers. Two basic chip organizations were considered. One chip organization was assumed to be equivalent to that of Ypma, Gergis, and Archer with a conventional major minor loop configuration. The other organization considered employed a major-minor loop configuration in which the minor loops were broken into two segments to facilitate stacking and implementation of multilevel hierarchies as suggested by Tung, Chen, and Chang. The analysis shows that a near optimum organization for 65,536-bit chips with segmented minor loops consists of 64 minor loops of 1024 bits with each minor loop broken into a 64-bit segment and a 960-bit segment. View full abstract»

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  • A high speed drive coil for a large capacity bubble memory

    Publication Year: 1976 , Page(s): 639 - 641
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    We calculated an eddy current loss in a wire as a function of an applied ac field. Estimating the field at an actual coil wire and summing the losses in all points of wires we obtained a formula representing a coil loss. Based on the calculated results, we designed coils which drive thirty-two 64 kb chips. The observed loss of the coils was in good accord with the calculated one. This 2 Mb module was operated at 40 Oe rotation field of 500 kHz with the coil loss of 8 W. View full abstract»

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  • Analysis of rotating fields in magnetic bubble drive coils

    Publication Year: 1976 , Page(s): 642 - 644
    Cited by:  Papers (1)
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    Closed-form normalized expressions for the field components inside a single-layer rectangular solenoid are derived from a model in which the solenoid is approximated by finite length current sheets of infinitesimal thickness. The equations are extended by superposition to include the case of a multi-layered solenoid, and the effects of nearby magnetic materials are included by employing the method of images. Computer generated field plots compare favorably with measured data. View full abstract»

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  • Relationship of bias field setting procedure to field stability against external field perturbations for magnetic bubble memory bias field structures

    Publication Year: 1976 , Page(s): 645 - 647
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    In magnetic bubble memory packages having a bias field HBsupplied by a Ba-ferrite permanent magnet structure, the magnitude of HBmay be appreciably altered after setting by transient exposure to externally applied magnetic fields Hextas much as 10 times smaller than the field used in setting HB. We examine this effect for a particular magnet design having a permalloy yoke, a gap of 0.270 inches, and a saturation field H_{sat} \simeq 240 Oe. We find that the magnitude of the effect depends upon the ratio H_{B}/H_{sat} and upon the procedure used in setting HB. After setting to H_{B} = 200 Oe from saturation with a demagnetizing field H_{ext} = -1400 Oe, a remagnetizing field H_{ext} \simeq 1800 Oe is required to increase HBby 1%. On the other hand, after setting to H_{B} = 100 Oe with H_{ext} = -2300 Oe, a remagnetizing field H_{ext} \simeq 400 Oe is sufficient to increase HBby 1%. Setting by demagnetizing from saturation yields superior stability to setting by magnetizing from the demagnetized state, and stability of the set magnet may be further improved by demagnetizing with a ringing (alternating) field. This behavior is explained with a simple model and its importance for magnet design is discussed. View full abstract»

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  • Temperature dependence of Ba-ferrite bubble memory bias magnets as a function of magnet geometry

    Publication Year: 1976 , Page(s): 648 - 650
    Cited by:  Papers (1)
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    The coefficient of the linear variation of field strength with temperature in Ba-ferrite is shown to have a simple functional dependence upon the permeance coefficient (B/H ratio) of the magnet structure. Using cylindrical magnets with aspect ratios of 0.030 to 4.00 and measuring the field strength from -35 °C to +65 °C, we observe temperature coefficients varying by about 40% from -0.150%/°C to -0.207%/°C These values have a simple relationship to calculated magnet permeance coefficients. An analog circuit approach is presented for calculating the permeance coefficients of complex bias magnet systems. The temperature coefficients predicted from the calculated permeance coefficients and the measured bias field temperature dependences are in good agreement. View full abstract»

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  • Gap tolerant bubble propagation circuit

    Publication Year: 1976 , Page(s): 651 - 653
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    A new bubble propagation pattern for field access devices has been developed which has a period to gap ratio of 8:1. In this pattern of semicircular elements (half-disk) the gaps are situated between essentially parallel poles in contrast to the TI pattern where gaps are located between orthogonal poles. The bubble, therefore, comes under the influence of two strong parallel poles causing it to stretch across the gap. The energy barrier that would normally be encountered thus virtually disppears. Devices of 32, 18, and 10 μm periods have been designed and fabricated. The results show a typical margin of at least 20% of the bias field under normal operating conditions. The operating drive field is relatively low for small bubbles. The minimum drive field for a 10 μm period pattern is only 13 Oe. View full abstract»

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  • Magnetic bubble device processing and pickax circuit design

    Publication Year: 1976 , Page(s): 654 - 656
    Cited by:  Papers (4)
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    The processing of Permalioy field-access magnetic bubble devices will be discussed for lead-first, double level circuits emphasizing 5 μm diameter bubble circuits, but with reference to scaling down the process to 2 μm bubble diameter circuits. Device structures will be presented with typical material thicknesses and processes used for each level. A new bubble circuit based on the pickax replicator and the pickax propagation element will be introduced with emphasis on the relaxation of processing constraints that this circuit provides. Also quasi-static propagation margins for several of the key pickax elements will be presented. View full abstract»

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  • Electroplated permalloy for bubble propagation and detection

    Publication Year: 1976 , Page(s): 657 - 659
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    A description is given of the fabrication conditions and magnetic properties of electroplated permalloy for bubble circuits. Propagation and detection elements are grown in stencils delineated in the resist. The plating base is a thin Cr-Cu layer which is chemically etched. A 2% magnetoresistive ratio is obtained with the 12% Fe composition yielding signals of 1 mV/mA. Propagation margins and detection signals are comparable to those given by circuits fabricated by vacuum deposition methods. View full abstract»

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  • Bubble propagation by disks formed by ion-implantation

    Publication Year: 1976 , Page(s): 660 - 662
    Cited by:  Papers (3)
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    The investigation of implantation conditions for bubble propagation points to the necessity for a minimum dose ( 1.5 \times 10^{16} ions cm2) and a sufficiently thick profile (0.4 μ). The use of flat profiles gives uniform implanted layers and allows values of the maximum defect concentration far away from the amorphization threshold. Unlike in permalloy circuits, bubble stability and bias field margins do not increase with the drive field. The propagation is not critically dependent upon disk diameter and spacing. View full abstract»

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  • Analysis of nonuniformity of bubble propagation in field access systems

    Publication Year: 1976 , Page(s): 663 - 665
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    The static and dynamic properties of bubbles can be conveniently observed by using a mirror overlay between a drive structure and a thin ferro-garnet film. This method was applied to studies of bubble propagation in T-bar, T-X and chevron permalloy drive structures. The results of the study lead to the conclusion that a parameter a should be introduced for estimating the nonuniformity of bubble propagation. This parameter is found by photometric measurements of light intensity variations along the bubble propagation path over the structure period λ and by subsequent calculations. View full abstract»

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  • Comparison of experimental and theoretical results for high frequency bubble propagation under T-bar tracks

    Publication Year: 1976 , Page(s): 666 - 668
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    Observational results for bubble motion at high frequencies in field-accessed devices have been reported in the literature. The predictions of a model for bubble propagation under T-bar tracks are compared with these results for a frequency of 100 kHz, initially at midrange values of drive and bias fields. This comparison is helpful in refining certain features of the model so as to bring its assumptions nearer to the physical situation. The matching between predicted and observed results for the variation of bubble position with drive field angle is now much improved. The refined model is then used to calculate results at other values of drive and bias fields for which experimental data is available. The agreement between theory and practice is shown to be quite close except when the bias field is high. View full abstract»

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  • Analysis of field access drive circuit and bubble interactions with the aid of Fourier series

    Publication Year: 1976 , Page(s): 672
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  • Proximity and interaction effects in arrays of I-bars

    Publication Year: 1976 , Page(s): 669 - 671
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    Calculations have been made of interactions and fields in two-dimensional periodic arrays of I-bars. The results of the study shed light on several questions of interactions among bubble propagation elements. We have calculated interaction effects in arrays of I-bars as a function of both longitudinal and transverse spacing between bars. Three different geometries of I-bar show similar effects; the transverse and longitudinal interactions have opposing signs and are stronger in the transverse direction. We also have calculated local and average fields for an array of I-bars of geometries chosen to facilitate comparison with recent measurements. The local field in the gap between elements is found to be highly nonuniform but with an average value that obeys a simple relationship as the gap length is varied. The field profile is also nonuniform in the transverse direction, and exhibits a proximity enhancement that depends upon gap dimension. These results support the interpretation that bar-bar interactions can influence the magnetization in propagation arrays. View full abstract»

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  • The effect of overlay stress on the uniaxial anisotropy of garnet bubble domain films

    Publication Year: 1976 , Page(s): 673
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    In the overlay films used for bubble domain propagation circuitry elastic energy is stored. Some of this energy is transferred to the LPE garnet film and because of the magnetoelastic coupling, significant alterations can be caused in the uniaxial anisotropy, Ku. The amount of elastic energy stored in the overlay is typically proportional to the product of the film stress and the film thickness. The elastic energy transferred to the garnet film is via surface tractions at the interface of the garnet and the overlay films. By assuming as boundary conditions that these surface tractions are uniform underneath the overlay and zero outside of the overlay boundaries, it has been possible to calculate from elasticity theory the stress distribution in the garnet film and substrate.The results show that the most severe alterations in Kuoccur at the edges of the overlay. Underneath the overlay the changes in Kuare less severe. 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