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Magnetics, IEEE Transactions on

Issue 4 • Date December 1969

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Displaying Results 1 - 25 of 36
  • [Front cover and table of contents]

    Publication Year: 1969 , Page(s): 0
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  • Richard M. Bozorth

    Publication Year: 1969 , Page(s): 690 - 691
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  • Advances in magnetics

    Publication Year: 1969 , Page(s): 690
    Cited by:  Papers (1)
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  • Basic research and applications in magnetism

    Publication Year: 1969 , Page(s): 692 - 700
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    Several brief case histories are recounted, to show how basic scientific discoveries of new materials and phenomena are used as necessary background for the design of modern devices. The essential elements in the follow-through from the discoveries to the useful devices are listed for six subjects used as examples: 1) rare earths for permanent magnets, 2) orthoferrite domain "bubbles" for memory, 3) Faraday rotation of polarized microwave radiation, 4) magnetic properties of grain-oriented silicon steel, 5) optical properties of magnetic materials, and 6) superconducting magnets. View full abstract»

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  • Magnetooptics, lasers, and memory systems

    Publication Year: 1969 , Page(s): 700 - 716
    Cited by:  Papers (15)  |  Patents (2)
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    The field of magnetooptics is reviewed and the application of a magnetic memory system as a readout technique is discussed. A review and comparison of the fundamental magneto-optic effects and their utility in a system is presented. It is shown for a longitudinal Kerr readout system that laser and shot noise limit wide-band (1 MHz) signal-to-noise ratios to about 40 dB. Media noise problems are reviewed. The limitations to packing density are discussed, and it is concluded that packing densities greater than 107bit/in2(including suitable guardbands) are practical. The various techniques for optico-thermal recording are surveyed. A discussion of related hardware components (such as optical modulators and lasers) is presented. It is concluded that a viable magnetooptic detection-laser beam memory system is practical. No suitable nonmechanical scanning system has yet been developed. View full abstract»

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  • Magnetic oxide films

    Publication Year: 1969 , Page(s): 717 - 727
    Cited by:  Papers (19)  |  Patents (1)
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    Polycrystalline and epitaxial magnetic oxide films have been fabricated by several investigators. This paper deals predominantly with epitaxial films grown by chemical vapor deposition. The majority of the discussion is concerned with substrates, the deposition process, and film characterization. Where possible, comparisons are made with bulk crystals and with films produced by other fabrication techniques. View full abstract»

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  • Plated-wire technology: A critical review

    Publication Year: 1969 , Page(s): 728 - 751
    Cited by:  Papers (13)
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    Electrodeposited cylindrical magnetic film memory technology is reviewed. Extensive references are made to previous work. New data is given in areas not previously reported. Special emphasis is given to the following items: 1) Applications: Plated-wire applications cover the spectrum from 100 to 1000 ns cycle time NDRO memories of 105to 107bits capacity in commercial and military markets. 2) Processing: Substrate preparation and electrochemical processing, as well as alternative magnetic plating solutions, and the control of pH, temperature, flow rate, Ni-Fe ratio, and other variables necessary for high yield plating are reviewed. 3) Aging: The conditions that stabilize the film and the test methods that predict a 10- to 100-year life are reviewed. 4) Testing: A practical approach to continuous production line testing is reviewed. 5) Bit Packing Density: Calculations on magnetization distribution along the wire are compared to experience. Although memory plane geometry is important, the wire characteristics dominate the achievable bit density. Wire diameter, film thickness Hk, and other factors are included in graphs useful for design purposes. 6) Memory Plane Construction: The relative advantages of several different forms are compared. The need for magnetic keepers and their advantages are reviewed. 7) Interactions: New data is presented on some of the effects of variations in word strap alignment and spacing as well as the sensitivity to variation in plated-wire spacing and bending. View full abstract»

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  • Soft magnetic thin-film memory materials

    Publication Year: 1969 , Page(s): 752 - 764
    Cited by:  Papers (3)
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    Thin-film deposition techniques as applied to magnetic memory applications are reviewed. The relationship between the microstructure of the film and the fabrication technique and pertinent parameters is discussed in terms of the atomistics of film nucleation and growth. The dependence of the magnetic properties governing switching of a magnetic storage element is qualitatively discussed in terms of the microstructure and ripple theory; literature data is used to elucidate this by showing the effects of composition, temperature, thickness, and substrate morphology on the magnetic properties. The literature values for the anisotropy field, coercivity field, and dispersion of various classes of ternary alloys is reviewed, extending previous papers reviewing elemental and binary alloys. View full abstract»

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  • Ferrite core planes and arrays: IBM's manufacturing evolution

    Publication Year: 1969 , Page(s): 764 - 774
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    IBM's manufacture of arrays is reviewed in the context of advances in manufacturing techniques that have been made over the past ten years. Early methods of winding core planes and array jumpering are discussed briefly, and the present status is viewed in more detail. View full abstract»

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  • Ferrite memory materials

    Publication Year: 1969 , Page(s): 774 - 811
    Cited by:  Papers (3)
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    A comprehensive review of the history and present status of ferrite memory materials is presented. The range of topics treated extends from the physical theories dealing with the origin of hysteresis loop squareness and the mechanism of flux switching to the technology of manufacturing memory cores. Themes that underlie the engineering, physics, and chemistry of memory cores are emphasized, particularly in respect to the material requirements for coincident current application. The limitations of memory cores and future prospects for this technology are discussed. Wherever possible an endeavor is made to syncretize, although in a critical and selective way, the sometimes conflicting theories and interpretations of experimental data. View full abstract»

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  • Permanent magnet applications

    Publication Year: 1969 , Page(s): 812 - 821
    Cited by:  Papers (3)  |  Patents (1)
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    The main uses of permanent magnets are covered either by the range of cast and magnetically treated alnico alloys or by the several grades of sintered barium/strontium hexaferrite, but minority materials have their special applications and continue to develop. Three different technical classes of permanent magnet applications can be distinguished. Firstly, magnets working in a magnetic circuit of static reluctance, e.g., speakers, moving-coil measuring instruments, microwave devices, separators, etc. Secondly, those working in a varying self-demagnetizing field due to change of circuit reluctance, such as clamping and holding magnets which range from planning-board indicators to large chucks for machine-tools. Thirdly, magnets which work in both a self-demagnetizing field and a varying externally produced field, as in motors, generators, the several types of magnetic couplings, and magnetic suspensions. For each of these three classes the basic design principles are indicated and typical applications are described. Additionally, there are uses for high-hysteresis permanent magnet materials without premagnetization, as in hysteresis motors. View full abstract»

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  • A critical review of magnetic recording materials

    Publication Year: 1969 , Page(s): 821 - 839
    Cited by:  Papers (14)  |  Patents (5)
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    A review of the methods of preparation and the relevant properties of materials which the authors consider suitable for incorporation in conventional magnetic recording surfaces such as tapes, disks, drums, strips, and cards is provided. This field is presently dominated by one material, gamma ferric oxide in fine particle form, and so it is not surprising that this material is discussed at greater length than its potential rivals. The reasons for this dominance are considered and found to be 1) the ability of gamma ferric oxide recording surfaces to perform adequately in the recording systems which have been developed so far, i.e., the magnetic properties of the oxide have apparently not been the limiting factors in the performance of recording systems; 2) the relative cheapness of the particles; 3) the existence of suitable binder systems of proven durability; and 4) the need for compatibility with existing recording devices. View full abstract»

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  • Semiconducting ferromagnetic spinels

    Publication Year: 1969 , Page(s): 840 - 848
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    The family of spinel compounds of which CdCr2Se4is the prototype has been found to be simultaneously ferromagnetic and semiconducting. Numerous experiments reveal, moreover, that the electronic states in these materials are strongly coupled to the degree of magnetic order. The interaction between the electronic transport and the magnetic state offers the exciting possibility of constructing electronic devices having magnetic control. This paper presents a review of literature on the magnetic, crystallographic, electrical transport, and optical properties of the chromium chalcogenide spinels as they relate to device applications. The prospects of realizing novel devices utilizing these properties are examined. View full abstract»

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  • Josephson-type superconductive tunnel junctions and applications

    Publication Year: 1969 , Page(s): 848 - 873
    Cited by:  Papers (12)  |  Patents (2)
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    The physics and applications of the Josephson effect are reviewed in detail. A brief introduction to superconductivity and tunneling is provided. The configuration most fully discussed is the oxide junction. However, properties of bridges, point-contacts, and solder-blobs are also described. Among the applications reviewed are magnetometers, infrared detectors, microwave generators and mixers, voltmeters, computer logic and memory devices, relaxation oscillators, thermometers, and spectrometers. View full abstract»

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  • Phase transitions, soft modes, and critical fluctuations

    Publication Year: 1969 , Page(s): 874 - 886
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    This paper gives an introductory review of the field of phase transitions. The first part contains a general discussion of the dynamical mechanism of phase transitions. The interactions between the particles are shown to yield a feedback effect in the collective response of the system to small external perturbations. This feedback provides the mechanism which can give rise to instabilities for certain critical values of the external parameters. It is pointed out how the static aspects of the instability (characterized by a singularity in the static response function) are intimately related to dynamic aspects, namely the occurrence of soft collective modes and of critical fluctuations. In the second part, the general picture is illustrated by a number of specific examples. Experimental results on soft mode behavior and critical fluctuations are shown for ferromagnetic, antiferromagnetic, ferroelectric, and structural phase transitions. It is further demonstrated that the existence of critical fluctuations near a phase transition gives rise to anomalous behavior of various physical properties of the system. Finally, some problems are indicated which arise in connection with instabilities occurring in nonequilibrium systems. View full abstract»

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  • Theory of linear superposition in tape recording

    Publication Year: 1969 , Page(s): 886 - 890
    Cited by:  Papers (25)
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    The conditions under which linear superposition (LSP) of isolated pulses is valid for the synthesis of multibit waveforms are examined theoretically. LSP is found to be valid subject to three conditions; first, that all the processes following the write process be linear operations on the tape magnetization; second, that the write field rise time be less than the bit interval; and third, that each change in magnetization, occurring during the write process, be a function only of the field causing that change. Additionally, the validity of LSP at 15 000 bit/in is demonstrated for a high resolution tape recorder using standard γ-Fe2O3tape. View full abstract»

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  • Influence of coating permeability in thin-film pulse recording

    Publication Year: 1969 , Page(s): 891 - 894
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    A modified model of M(H) curves which uses a more realistic family of minor loops has been designed for a theory of pulse recording. The loops are defined by the initial and maximal permeability, \mu a and \mu m , as well as by the reversible permeability \mu r of the tape. The calculation of the demagnetizing field, the magnetization transition, and the effective flux through the reproduce head is carried out by solving the Poisson differential equation, taking into account the boundary conditions of a two-dimensional head model. The calculation is carried out for an isolated linear magnetization transition of nonzero width. It results in Fourier integrals, the solution being provided by series expansion or approximation. The pulse amplitude and pulsewidth are given as simplified analytical functions of the tape permeability. View full abstract»

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  • A method for calculating hysteresis loops of interacting single-domain particle systems in a nonmagnetic binder

    Publication Year: 1969 , Page(s): 895 - 898
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    A method is given for calculating the minor and full hysteresis loops of a system of uniaxial single-domain particles with a common direction of easiest magnetization. A probabilistic approach is used in formulating the problem by means of two differential equations which are solved for the simple case of an infinite particle chain. The method is based on a model in which each particle is characterized by a rectangular hysteresis loop with a specific saturation field Hs, and the loops are influenced by the (homogeneous) external magnetic field H as well by the magnetization-dependent interaction of the particles among themselves. View full abstract»

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  • Hot pressed GdIG for magnetooptic memory application

    Publication Year: 1969 , Page(s): 898 - 901
    Cited by:  Papers (3)
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    This paper describes the preparation of polycrystalline GdIG by hot pressing and reports the most relevant properties of the material. Hot pressed samples were prepared using various conditions of time (1 to 20 hours), temperature (900 to 1300°C), and pressure (300 to 1000 kg/cm2). Dense specimens with grain diameter ranging from 1 to 10μm were prepared. Thin wafers made by sectioning and polishing samples have high coercive field (higher than 200 Oe), good hysteresis loop squareness ( Br/Bm = 0.85 ), and high figure of merit ( 2\beta /\alpha \sim 2 ). These properties make them well suited for optical mass memory application. This was confirmed experimentally, and a bit density of 5 \times 10^{5} bit/cm2was obtained by laser beam thermomagnetic writing. View full abstract»

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  • Hard magnetic two-phase Co-Cu thin films

    Publication Year: 1969 , Page(s): 901 - 904
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    The magnetic properties of sputtered films of 25 Co-75 Cu and 50 Co-50 Cu before and after annealing were investigated. In the as-sputtered state the films exhibit the structure of a metastable fcc solid solution. Annealing at 500 to 700°C causes decomposition into two phases, Cu and fcc 89 Co-11 Cu. The decomposition supposedly occurs by heterogeneous nucleation at the grain boundaries, and growth by grain boundary diffusion. The 89 Co-11 Cu phase exists in the form of small particles with magnetic single domain behavior. The films have coercivities up to 280 Oe. Squareness ratios between 0.7 and 0.9 were found. No strain sensitivity of the magnetic properties could be detected. This material is regarded to be suitable for magnetic recording. View full abstract»

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  • Frequency tripler with very little input-current distortion

    Publication Year: 1969 , Page(s): 905 - 908
    Cited by:  Papers (1)
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    A three-phase output frequency tripler is presented which operates with very little input-current distortion. In a conventional frequency tripler, filters for eliminating the higher harmonics in the input current must be placed in the primary lines. The frequency tripler described in this paper has a mechanism which suppresses the higher harmonics. View full abstract»

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  • An unorthodox transformer for free-running parallel inverters

    Publication Year: 1969 , Page(s): 908 - 912
    Cited by:  Papers (4)
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    Limitations imposed on free-running parallel inverters by the interdependence of critical characteristics of the networks, transformers, and switching elements of these inverters are identified. The transformer's role within these networks with abruptly changing circuit configurations is related to the network's functional mechanism. Special attention is devoted to forms of "volatile" returnable energy stored within the intended paths of magnetic flux and to magnetic saturation effects in pertinent transformer cores that cause harmful current spikes at the termination of individual cycles of operation. Returnable magnetic energies stored in representative "square loop" iron and ferrite transformer cores per unit of volume, and in related air gaps are calculated and tabulated for comparison and reference. A method for mitigation of storage of unwanted magnetic energy and for the prevention of magnetic saturation in inverter transformer cores is presented; it is reinforced with quantitative relations and a report on experimental work. View full abstract»

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  • A 1.5 × 105bit low-current high-speed planar-magnetic-film memory with high-storage density

    Publication Year: 1969 , Page(s): 912 - 917
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    The access and cycle time limits and storage capacity limits of a DRO memory with planar magnetic films are estimated. Basing on these estimates, the concept of a magnetic-film memory of high-storage density is developed which operates on low-drive currents and allows high operating speeds. The magnetic films, the storage element structure, and the drive lines required for realizing the memory plane are treated. Data of a realized feasibility model, which deviate from conventional values (word line period 200 μm, digit line period 300 μm, nominal word current 120 mA, nominal digit current 32 mA, delay times on the lines of the plane 3 ns for a storage capacity of 1024 words of 144 bits each) are explained. The memory electronics and the status of development are reviewed. View full abstract»

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  • Fabrication of grouped magnetic heads

    Publication Year: 1969 , Page(s): 918 - 920
    Cited by:  Papers (2)
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    A new magnetic transducer has been developed for use in the measurement of mechanical displacement. Experiments suggest that the transducer could be used for various purposes: for instance, readout information from magnetic drums or disks of computers, nondestructive readout from thin-film memories, magnetic pattern recognition, and an unconventional flux sensor. The transducer is composed of flux-sensitive magnetic heads which are fabricated from a sheet of ferromagnetic thin film by photoetching process. By using the etching process, a large number of heads are produced simultaneously, and the heads are operated in a group. The characteristics, performances, and an application of grouped magnetic heads are described in this paper. View full abstract»

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  • Torque exerted on anisotropic magnetic medium by electromagnetic wave

    Publication Year: 1969 , Page(s): 921 - 924
    Cited by:  Papers (1)
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    The possibility of exerting a torque with a nonzero time average value as a result of interaction of a plane electro-magnetic wave with anisotropic magnetic medium is discussed. The torque per unit volume produced by the action of the magnetic field on the magnetization of the medium is T = M \times H and it arises from the fact that the vector of magnetization M is in general not parallel to the magnetic field intensity H . Three cases of magnetic media are distinguished: 1) medium with a natural or static anisotropy, 2) gyrotropic medium, 3) medium with shape anisotropy. In the first case, the lossless medium having a permeability \mu x, \mu y in the x and y directions perpendicular to the direction of electromagnetic plane wave propagation, the maximum of the torque per unit area corresponds to the thickness of the section \Delta z = \lambda _{0}/2(nx - ny) , where nx,ny are the refraction constants of the medium, and the sign of torque is opposite in the neighboring sections. In the case of a gyrotropic medium characterized by Polder's permeability tensor, it can be shown that the average value of torque exerted on a lossless medium by a plane wave propagating in the direction of dc magnetic field is zero. The nonzero average value of torque exists in the case of gyrotropic medium with losses as in the third case when a plane linearly polarized wave propagates along a ferrite cylinder with elliptical cross section. The results of not yet finished experimental investigations, which had to confirm the possibility of utilization of the torque for the construction of a feed-through wattmeter for the measurement of microwave power in the X band, are shown at the end of the paper. 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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Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology