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Magnetics, IEEE Transactions on

Issue 1 • Date March 1974

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Displaying Results 1 - 22 of 22
  • [Front cover and table of contents]

    Publication Year: 1974 , Page(s): 0
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    Freely Available from IEEE
  • Magnetooptical properties of ferrimagnetic CoCr2S4in the near infrared

    Publication Year: 1974 , Page(s): 2 - 7
    Cited by:  Papers (2)
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    CoCr2S4, which is a ferrimagnetic insulator, has been prepared by hot-pressing microcrystalline powder. The infrared magneto-reflectance effects have been measured at several temperatures below the transition temperature of 221K. Very large Kerr effects, which are centered at 1.0 and 1.7 μm, have been associated with the principal crystal field transitions of divalent cobalt. These samples exhibit a normal remanence of at least 95 percent, which is attributed to strain-induced anisotropy in the sample. The transmission and Faraday rotation of the material are deduced from Kramers-Kronig and other analysis of the reflectance data. The use of this material in a digital-storage application is discussed View full abstract»

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  • Electromagnetic coupling between two parallel layers of yttrium iron garnet for microwave device applications

    Publication Year: 1974 , Page(s): 7 - 11
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    An X band microwave filter consisting of two microwave cavities attached and orthogonal to each other with a YIG-GGG-YIG sample in a sandwich configuration has been designed and tested. Normally the two cavities do not couple electromagnetically to each other, but do couple through the sandwich configuration. The sandwich configuration is placed in between the two cavities so that there is one YIG film in each cavity. The amount of coupling can be varied by: (1) the magnitude of the static field, |\over\rightarrow{H}| , and (2) the angle between \over\rightarrow{H} and the film surface. The parallel layering of the two YIG films is essential in the improved performance of the microwave filter. View full abstract»

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  • Wave propagation along domain walls in magnetic films

    Publication Year: 1974 , Page(s): 11 - 17
    Cited by:  Papers (2)
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    It is shown by theoretical analysis that domain walls can support two different types of waves denoted as "magnetostatic interface waves" and "wall displacement waves". The magnetostatic interface waves are similar in character to magnetostatic surface waves. The wall displacement waves are analogous to displacement waves on strings and to capillary waves on the surface of liquids, Dispersion relations are derived for both types of waves. The displacement waves are approximately dispersion free at high wavenumbers. At low wavenumbers their dispersion diagram reflects the incipient instability of the straight domain wall against sinusoidal displacement, which occurs as the field gradient is reduced. View full abstract»

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  • "Lorentz" microscopy of stripe domain films with protons

    Publication Year: 1974 , Page(s): 18 - 22
    Cited by:  Patents (1)
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    A new method is reported for observing the in-plane component of magnetic structure in stripe domain films. Stripe domain films act as a Faraday-effect diffraction grating, and deflect light beams in a way reminiscent of electrons being deflected by the Lorentz force in a magnetic thin film. The direction of the stripes is that of the local in-plane magnetization vector. Thus the angle of deflection is perpendicular to the local in-plane magnetization, as is the case for Lorentz deflection. Micrographs are presented demonstrating that with a displaced aperture one can perform with light the analogues of the two modes of Lorentz microscopy: light-field microscopy in the defocused mode and dark-field microscopy with light normal to the film plane. In the defocused mode, walls appear as either bright streaks or dark streaks; if one focuses on the opposite side of the film the bright walls become dark and vice-versa. In the dark-field mode the contrast of the dark regions and the bright regions can be reversed by moving the aperture. View full abstract»

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  • Characterization of magnetic bubble generators

    Publication Year: 1974 , Page(s): 23 - 27
    Cited by:  Papers (2)  |  Patents (1)
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    Two types of magnetic bubble generators suitable for a field-access bubble memory have been tested at 1.00 kHz bit rate at in-plane rotating fields above 15 Oe. The bias field margins of the generators at 30 Oe rotating field are equal to or greater than those of loop propagation. Both designs are based on the principle of stretching and cutting seed bubbles circulating around a Permalloy disk. Functions of stretching, cutting and transferring in the generator sequence are accomplished either with Permalloy elements or pulsed current conductors. The operating conditions of the generators in terms of current pulse amplitudes, widths and phase angles are presented. Among the two designs, namely Permalloy-stretch and conductor-stretch generators, the latter has a wider phase-angle margin. View full abstract»

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  • Nonlinear domain-wall velocity and coercive force in permalloy films

    Publication Year: 1974 , Page(s): 27 - 31
    Cited by:  Papers (2)
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    Domain wall velocities are measured for 2700 Å and 2200 Å thick Permalloy films of several coercive forces. The velocity-drive field curves are characterized by two mobilities, as often reported. It is found that these low- and high-field mobilities are strongly affected by coercive force of the films. The low-field mobility is nearly constant for low-coercive-force films, and decreases rapidly with increasing coercive force. The high-field mobility is inversely proportional to the coercive force. The measured results suggest that the nonlinear dependence of wall velocity on drive field would disappear in a zero-coercive-force film. None of the mechanisms proposed up to now can explain this behavior of wall velocity in Permalloy films. The nonlinearity is attributed to the transition of material inhomogeneities from pinning centers in low field to dissipation centers in high field. View full abstract»

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  • Influence of coercive force and easy-axis bias on domain wall motion in NiFeCo films excited by hard-axis pulses

    Publication Year: 1974 , Page(s): 31 - 36
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    Domain wall motion in vacuum-deposited 1200 Å- 2000 Å-thick NiFe and NiFeCo films, excited by a 0.5 ns rise time/200 ns fall time hard-axis pulse field with an easy-axis dc field, is examined with regard to coercive force, easy-axis bias, and low-frequency creep results. Both NiFe and NiFeCo films have the same threshold field characteristics despite large differences in properties. The magnitude of the hard-axis pulse field necessary to cause creep increases with increasing difference between wall coercive force and easy-axis bias. Furthermore, the average creep displacement, for a given hard-axis pulse field magnitude, versus the easy-axis bias field normalized by wall coercive force results in almost identical curves for both NiFe and NiFeCo films except for a shift related to the threshold field. This result is consistent with previous low-frequency creep data and implies that the basic mechanism of low- and high-frequency creep may be closely related. The direction of the basic wall motion depends on the spin polarity in the wall and the durection of the hard-axis pulsed field. Motion in a direction opposite to the basic motion may be produced by an esay-axis bias field of sufficient magnitude but less than then wall coercive force, which is a new and significant result. A theory based on the dynamic torque equation and nonconservative spring coercive force model has been developed to explain the high-frequency creep phenomenon. This theory qualitatively predicts the observed experimental results very well. View full abstract»

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  • Movement of an individual Bloch wall in a single-crystal picture frame of silicon iron at very low velocities

    Publication Year: 1974 , Page(s): 36 - 38
    Cited by:  Papers (5)
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    The movement of an individual Bloch wall in a single-crystal picture frame of silicon iron was studied. By using an electronic apparatus the wall velocity was held constant during the magnetization reversal. It was possible to control the wall velocity down to 10-2mm/s. Even at these low velocities the relationship between the wall velocity v and the driving magnetic field H is precisely linear: v = const . (H-H_{0}) . This is to be expected under the given experimental condition dB/dt = const . View full abstract»

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  • Statistical properties of magnetization discontinuities in technical steels

    Publication Year: 1974 , Page(s): 39 - 43
    Cited by:  Papers (1)
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    The application of statistical methods to the study of technical steels is described and a statistical amplitude distribution function for the magnetization discontinuities is presented, making use of the correlation between the amplitudes observed and the structure of the material. It is shown by experimental measurements that the optically measured grain size distribution of fine-grain low-carbon steel correlates closely over a wide range with the distribution of the pulse heights measured. The results of previously performed measurements have been investigated statistically using a multichannel analyser, and these pulses are shown to obey Weibull's distribution. The physical characteristics of the distribution function of the magnetic discontinuities and its computed parameters are discussed. View full abstract»

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  • A new surface transducer for generating and detecting magnetic field transients in ferromagnetics

    Publication Year: 1974 , Page(s): 44 - 50
    Cited by:  Papers (2)
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    A new surface transducer is described for generating and detecting magnetic field transients or magnetization discontinuities in ferromagnetic materials [8]. The sensing is based on searching for transients of the magnetic potentials which would be likely to occur on the surface of the specimen. A coil core of high-frequency ferrite is used for this. The sensor theory presented shows the coaxial geometry of the coil core to be that which is more practicable for limiting detection to a compact volume of the specimen to be analyzed. The fundamental noise and disturbance analyses performed show adequate margins for wideband noise and external stray field disturbances. The transducer electronics for generating the varying external magnetic field in the specimen and for detecting the occurring field transients are described with a view to the optimization of the electrical circuits, and the resulting specifications are discussed. The surface transducer constructed is widely applicable for studying the magnetization characteristics of different ferromagnetics nondestructively in conjunction with stochastic-ergodic analyzers such as a pulse-height analyzer or a digital correlator through a punch-tape recorder or in on-line connection with a computer [7]. View full abstract»

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  • Variation with specimen size of some properties of Alcomax III at 50 Hz excitation

    Publication Year: 1974 , Page(s): 50 - 54
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    When subjected to dynamic excitation at 50 Hz with sinusoidal field intensity, the power loss per unit volume, coercive force and remanent flux density of square-section specimens of Alcomax III were found to be functions of specimen size. At fixed excitation the coercive force increased and the remanent flux density decreased both as linear functions of specimen section side dimension. Loss per unit volume at low field intensities decreased as specimen size increased and was less than that calculated from the static B/H loops. With high field intensities the loss per unit volume increased with increase of specimen size and was in excess of that predicted by the static B/H loops. View full abstract»

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  • Transient phenomena in magnetic circuits having components of solid ferromagnetic material

    Publication Year: 1974 , Page(s): 54 - 59
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    In solid ferromagnetic parts of magnetic circuits, eddy currents occur during changes of the magnetic flux. Magnetic circuits of real devices may often be decomposed into parts having approximately rectangular or circler cross sections. As the solutions for phenomena in infinite configurations of such cross sections are known, we can use these for solving phenomena in more complicated arrangements. The method described in this paper is based on the use of Duhamel's integral. This method enables one to solve phenomena in such magnetic circuits, which are composed of both parts made of solid ferromagnetic materials and parts made of materials in which no eddy currents may occur. The method is convenient for transient phenomena but may also be used for cases with periodic non-sinusoidal exciting currents. Some examples are given. View full abstract»

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  • Theory of magnetographic printing

    Publication Year: 1974 , Page(s): 60 - 69
    Cited by:  Papers (3)
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    The magnetic force of attraction between a recording surface and magnetic particles (the "developer" or "toner") is analyzed. The recording medium is assumed to be magnetically hard, the toner particles to be magnetically soft. The distribution of recording magnetization is taken to be periodic in the interior of an image area and uniform in an image free area. The toner particles are assumed to be part magnetic, part nonmagnetic material. In most of the calculations it is assumed that the magnetic susceptibility of the toner particles is small compared to unity. In the interior of an image area the force density has primarily a component perpendicular to the recording plane. This component decreases exponentially with distance from the recording plane, if the distribution of magnetization is sinusoidal. Near the edge of an image area the force density also has a tangential component, but this is generally smaller than the normal component. For toner particles with similar internal structure the force per unit mass always decreases with increasing particle size. Considered as a function of recording wavelength (at constant particle size) it shows a maximum at a wavelength comparable to the particle diameter.The force acting on a small particle ( \simeq 10\mu m) in the immediate vicinity of the recording surface can be several hundred times the force of gravity. The implications of these results in regard to color printing are discussed. View full abstract»

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  • Applications of Fourier transforms in digital magnetic recording theory

    Publication Year: 1974 , Page(s): 69 - 77
    Cited by:  Papers (4)  |  Patents (1)
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    In this paper we present a unified treatment of many problems in digital pulse recording. The physics appropriate to each problem is characterized by a reciprocal-space transfer function, which may be abstracted from published studies of sine wave recording. Over twenty-five transfer functions are given in appendices. Given the transfer functions, an inverse Fourier transformation completes each problem. The fields, fluxes, and output voltage due to an arctangent magnetization profile in a tape of unit permeability are derived. A closely related case, that of a linear ramp magnetization, is treated briefly. A step function magnetization is considered for a tape of nonunit permeability in which, dependent upon the boundary conditions, demagnetization and remagnetization occur. Extensions of the theory of multitransition waveforms are undertaken, yielding the spectra of both regular and random sequences. View full abstract»

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  • Selected characteristics of plated wires from various sources

    Publication Year: 1974 , Page(s): 78 - 88
    Cited by:  Papers (1)
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    Plated wires, 2.5 and 5.0 mils in diameter, have been obtained from various sources and compared to our own 2.5 mil diameter wire made on both copper-beryllium and tungsten substrates. The wires have been tested for their digit, word, and shmoo windows, pulse output and uniformity of output, skew and magnetostriction and their uniformity, the tension and torsion stress changes in the above characteristics, the thickness of the magnetic layer, stability during accelerated aging, and their mechanical characteristics. The characteristics of the wires in the unstressed condition were all adequate for memory application. Differences in signal output and location of the operating windows could be correlated with differences in film thickness and wire diameter. Pulse signal fluctuations were found to be directly proportional to magnetostriction fluctuations. There were great differences observed in the behavior of the samples under stressed conditions. These differences were shown to arise from differences in the local fluctuations in magnetostriction, the modulus and diameter of the substrate, and differences in the metallurgical and magnetic structure of the permalloy film. Accelerated aging showed 2:1 differences in rate between some samples. View full abstract»

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  • Analog memory devices based on NDRO toroidal cores

    Publication Year: 1974 , Page(s): 89 - 92
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    Discussed are the main aspects of operation, physics, design, and application of toroidal cores as nondestructive read-out analog memory elements. The analog memory element and switch are the basic components of the analog memory device of the open-loop type (i.e., without negative feedback). The toroidal core has been shown, both theoretically and experimentally, to exhibit linear read-write characteristics in pulse remagnetization. Diode switches are the most preferable for writing analog information. Analysis of the output and read circuits required to determine the optimal value for the read circuit resistance is given. The complex studies carried out resulted in a simple analog memory device with ± 3 percent error and the write time of 0.3μs. Ways to improve these parameters are described. View full abstract»

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  • A note on the magnetostrictive ringing in core memory systems

    Publication Year: 1974 , Page(s): 93 - 94
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    The observed ringing voltages in core memory systems depend on the frequency and the width of the pulsed current inputs. The pulse-width dependence results in maxima and minima, and the frequency dependence also results in maxima and minima in the peak amplitude of the ringing voltages. These phenomena have been examined and analyzed by a superposition of waves excited by fields due to the rise time and the fall time of all pulsed current inputs. The results show that a proper choice of the current width can be helpful in canceling the ringing voltages in the core memory systems. View full abstract»

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  • Poisson's and Laplace's equations in inhomogeneous magnetic media

    Publication Year: 1974 , Page(s): 94 - 96
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    Poisson's equation in inhomogeneous static magnetic media is derived for the magnetic vector potential and for the magnetic scalar potential. A modified three-dimensional seven-point finite-difference operator to be used in numerical solutions is presented. The special case of discrete inhomogeneity as discussed. View full abstract»

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  • Method of forming ferrite impregnated resins for microwave measurements

    Publication Year: 1974 , Page(s): 96 - 97
    Cited by:  Patents (3)
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    An inexpensive, reproducible technique for forming films and slabs of ferrite and carbonyl iron loaded polyethylene has been devised. The advantages of this technique are 1) uniform distribution of the powdered material in the resin binder, 2)smooth and flexible specimens of predetermined thickness and dimensions, and 3) reproducible magnetic and dielectric data. View full abstract»

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  • [Back cover]

    Publication Year: 1974 , Page(s): 0
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    Freely Available from IEEE
  • Axifield

    Publication Year: 1974 , Page(s): 98
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    First Page of the Article
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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