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Magnetics, IEEE Transactions on

Issue 2 • Date June 1973

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

    Page(s): 0
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  • MnBi films for magnetooptic recording

    Page(s): 66 - 83
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    Progress made during the past years in the area of magnetooptic data storage by the computer industry has been most impressive. Many material media and physical phenomena have been developed for this particular application. It now appears that a large capacity (gsim 10^{10}bits) magnetooptic data store possessing major advantages over the conventional recording techniques could be developed. Of the many materials and techniques advanced to date, the use of thin films of MnBi for thermomagnetic writing, erasing, and magnetooptic reading has received particularly intensive study because of the many unique properties of this film medium. In order to provide an assessment of the potential of this medium for optical memory application, we have included in this review the pertinent material physical properties of MnBi; the memory characteristics in regard to read, write, and erase operation; the physical process involved in the writing and erasure by thermomagnetic technique; the technique for detection of written information; and the utilization of this medium for magnetic holographic storage. Emphasis is given to the material properties and physical phenomena, rather than the systems considerations in using MnBi films for optical memory. View full abstract»

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  • Holographic read-write memory and capacity enhancement by 3-D storage

    Page(s): 83 - 94
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    The capacity and limitations of fast random-access holographic memory are discussed. Capacities such 1011bits can be envisioned by superposition of holograms in a thick erasable storage material. The organization of the read-write holographic memory provides the possibility of varying the reference beam angle at any given point of the memory plane. View full abstract»

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  • Magnetic measurements with the rotating-sample magnetometer

    Page(s): 94 - 109
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    The general features common to all rotating-sample magnetic measurements are described, and the governing equations are given. A number of cases of special interest are discussed in some detail: these include the measurement of magnetization as a function of field and temperature and the measurement of rotational hysteresis, various kinds of anisotropy, and magnetostriction. The concept of the rotating sample magnetometer is not new, but the method has greatly increased in practical value because of the development of the lock-in amplifier. The rotating-sample magnetometer method has many points of similarity to the vibrating-sample magnetometer. It is superior to the vibrating-sample magnetometer for some purposes, notably for anisotropy and magnetostriction measurements, and is generally simpler to construct. View full abstract»

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  • A compensating method of skew determination in cylindrical thin magnetic films

    Page(s): 110 - 111
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    A new compensating method for skew measurement in toristor-type cylindrical magnetic films is described. The state of the magnetization vector is scanned with a bipolar magnetic-field pulse and a compensating dc field is applied. Both the magnitude and direction of the skew are obtained. View full abstract»

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  • Magnetic field distribution in a ferromagnetic conductor

    Page(s): 111 - 113
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    The magnetic field distribution in a cylindrical ferromagnetic conductor is determined for the case of a direct current flowing along the axis of the cylinder and a constant external magnetic field applied in a direction transverse to the current flow. The Gauss-Seidel iteration method is employed to obtain the vector potentials for different values of current and external field with the aid of a digital computer. The magnetic fields are then calculated from the resultant vector potentials. Calculations are carried out for currentI = 1.5A, radius of the cylindera = 2mm, and external magnetic fieldB_{0} = 0to 0.6 Wb/m2. View full abstract»

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  • Flux distribution and power loss in the mitered overlap joint in power transformer cores

    Page(s): 114 - 122
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    The design of the joints in a power transformer core has a marked influence on the efficiency of the core as a whole. Two experimental cores have been built such that the lengths of their 45° mitered overlaps could be varied from 0 to 2.0 cm. The larger core, with 1.0 m limbs, was used for investigating flux and loss variations and the second, smaller core was used to study how the results might be affected by changes in dimensions. For the larger core, the power loss was measured in two ways for a range of overlaps: first, using the localized power loss technique, and then by measuring the total power loss with a precision wattmeter. In both cases, a minimum power loss was found when the core was built with an overlap of 0.5 cm. The overlap length was varied in the smaller core and again a minimum power loss was found, but with a 1.0 cm overlap. A change in loss of over 20% was found for the range of overlap lengths used, and the optimum overlap length was independent of flux density over the range from 1.0 T to 1.8 T. The special flux distribution was determined from an array of search coils. The variations in flux distribution enables a qualitative explanation of the occurrence of the minimum in power loss. View full abstract»

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  • A statistical model for the total AC core loss of lamination steels

    Page(s): 122 - 124
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    The total core loss at 15 kG induction of different types of nonoriented lamination steel is described empirically as a single function of thickness, grain size, resistivity, and a quantity related to the preferred orientation of the material. This texture-related quantity is the induction at 30 oersted, B30, divided by the saturation induction, BS. In addition, a linear effect of oxygen content on core loss is described for a more restricted group of materials. View full abstract»

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  • Optimum permanent-magnet dimensions for repulsion applications

    Page(s): 125 - 127
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    The repulsive force between identical right-circular-cylindrical permanent magnets is calculated, and the ratio of this force to the weight of a magnet is maximized through optimization of magnet size and shape. It is assumed that the magnets are uniformly magnetized along their axes. For magnets of thicknesstand radiusR, separated by a distance2h, the optimum dimensions areR = 3.45handt = 2.7h. For these dimensions, the repulsive magnetic force has the value2.65 mu_{0}M^{2}h^{2}newtons, with the magnetizationMin At/m andhin meters. View full abstract»

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  • The effect of interactions on the saturation remanence of particulate assemblies

    Page(s): 127 - 133
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    The effect of interactions on the saturation remanence of assemblies of identical, uniaxially anisotropic, single-domain particles is calculated using a spatial-mean interaction field. The particle easy-axis directions are assumed known and given by a distribution function. The remanence is determined by finding the magnetization orientation functional of the particle easy-axis orientation which minimizes the total assembly energy. Curves of remanence versus interaction strength (assembly packing fraction) are shown for a) randomly oriented assemblies of spherical particles with uniaxial crystalline anisotropy only, b) randomly oriented assemblies of acicular particles with shape anisotropy, and c) oriented assemblies of acicular particles with 6:1 aspect ratio. Disregarding external sample-shape demagnetization effects, this model always yields increased remanences due to interactions. A criterion is given which predicts when external shape effects are capable of dominating the net interaction field to yield a reduction in remanence. The applicability of these results and extensions of the theory are discussed in relation to particle assemblies in magnetic tape and high coercivity CoNiP films. View full abstract»

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  • An experimental investigation of the effect of medium thickness and transducer spacing on the read-back signal in magnetic recording systems

    Page(s): 133 - 139
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    An experimental investigation has been made of the dependence of the read-back signal on medium thickness and read transducer spacing for magnetic recording particulate disk file systems using saturation recording. The novel technique employed permits the study of the effects of transducer spacing and medium thickness without the need for changing either the medium specimen or the read transducer. For the ranges of transducer spacing (1.25-6.0 μm) and medium thickness (0.0- 1.75 μm) investigated, excellent agreement with theoretical predictions was found for peak signal amplitudes and half-pulsewidths of isolated pulses. It was also found that the -6 dB pulse packing density, calculated from half-pulsewidth measurements of isolated pulses, agrees well with experimental results. View full abstract»

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  • Head fields of asymmetric recording heads

    Page(s): 139 - 140
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    Head fields of asymmetric recording heads have been measured using 5000:1 enlarged models. From these measurements the head field gradients have been derived and are discussed in view of the role of this quantity in the recording write process. View full abstract»

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  • Information on computer program descriptions

    Page(s): 141
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  • [Back cover]

    Page(s): 0
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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