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Magnetics, IEEE Transactions on

Issue 2 • Date June 1965

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Displaying Results 1 - 13 of 13
  • [Front cover and table of contents]

    Publication Year: 1965 , Page(s): 0
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    Freely Available from IEEE
  • Administrative committee members

    Publication Year: 1965 , Page(s): 83
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  • A general frame for the displacement model of magnetization in ferromagnetics and some of its consequences

    Publication Year: 1965 , Page(s): 84 - 87
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    This author has shown previously that, by the proper use of the Lagrangian Function density method, a set of equations analogous to Maxwell equations for the ferromagnetic medium is obtained, involving an additional term, called "structural currents density," in the \nabla xH equation. Thus, the material macroscopic parameters appear to be not the constants assumed a priori (as in classical electrodynamical analyses), but can be determined for the medium considered by taking into account the structural energies involved. The solution of the problem for the case of the plane EM wave, identified with the plane individual 180° Bloch wall, leads to the new generalized equation of motion regarding both electrodynamical as well as structural and primary magnetic aspects. Certain well-accepted views are criticized here on the role of the eddy current and the viscuous damping of Bloch wall motion, especially with respect to magnetic diffusion damping. In this paper, the generalized equation of Bloch wall motion is solved for the case of irreversible displacement essential to nonlinear magnetic applications and theory. However, the applicability of the model developed is much broader, encompassing the characterization of magnetic materials under arbitrary magnetization conditions, whenever Bloch wall motion cannot be neglected. View full abstract»

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  • A magnetic amplifier for the visual presentation of low-frequency hysteresis loops of very small ferromagnetic samples

    Publication Year: 1965 , Page(s): 87 - 90
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    This paper describes a magnetic amplifier based on the principle of permeability tuning, and intended for the amplification of small, low-impedance signals obtained from a small ferromagnetic sample (e.g., a ferrite memory core or a thin film). The apparatus is able to produce a good display of a flux as low as \Delta \phi = 10^{-12} V/s at 50 c/s. In this case, the signal power applied to the amplifier is of the order of 10-16watts. View full abstract»

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  • An experimental study of flux presetting-resetting characteristics of magnetic cores with rectangular hysteresis loop

    Publication Year: 1965 , Page(s): 91 - 95
    Cited by:  Papers (1)
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    When magnetic cores with a square hysteresis loop are used for a time delay Crcuit or a pulse counter circuit, and if these circuits are designed by the use of the static hysteresis loop, the ac magnetization curve, or the control magnetization curve (CMC) which is the basic characteristic of a magnetic amplifier, there is apt to be a marked discrepancy between their design values and measured values. Since, in the flux control of magnetic cores used for a time delay circuit or a pulse counter circuit, the flux, contrary to the case with a magnetic amplifier, arrives at the negative saturation from the positive saturation by many intermittent signal voltages, a new characteristic quite different from CMC and other characteristics must be adopted as the standard of the design in this case. It was for this reason that instantaneous relation between the rate of flux change and the exciting current was examined in the case in which real flux resetting behaviors of a time delay circuit or a pulse counter circuit were taken into consideration, by using grain-oriented 50 per cent permalloy as the sample, with a view to obtaining core characteristics serviceable enough for exact design methods of a time delay circuit or a pulse counter circuit. Various useful results have been obtained as to: 1) how the correlation between rate of flux change d\Phi /dt and instantaneous values of exciting current icchanges in proportion to the flux values, 2) how the amount of reset flux \Delta \Phi _{r} will change according to the flux value \Phi and the rate of flux change d\Phi /dt , and 3) how the above-mentioned relations are connected to the tape thickness of the magnetic core. This paper reports the results of this investigation. View full abstract»

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  • The characteristics of ferrite cores with low Curie temperature and their application

    Publication Year: 1965 , Page(s): 96 - 100
    Cited by:  Papers (9)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The utility of ferrite cores which have the Curie temperature in the vicinity of the room temperature and suddenly change the permeability vs. temperature characteristic near the Curie temperature is described in this paper. Using the characteristics of these ferrite cores, the author made an overcurrent relay and a long delay circuit, and investigated their application to a temperature control device and to the thermomagnetic generator. These devices are smaller than usual, and operate with good accuracy. The author finds that ferrite cores with low Curie temperature are materials important to the development of a new field in electrical engineering. View full abstract»

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  • An investigation of separation losses in high-speed, high-density recording tapes

    Publication Year: 1965 , Page(s): 101 - 104
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The trend in digital tape recording is toward larger storage capacity and faster accessing, which necessitate packing information at greater densities on tapes moving at higher speeds. The losses that inevitably arise from the finite separation between the head and the moving tape become much more serious as the length of the magnetized regions in the tape is reduced and as the relative velocity of head and tape is increased. The purpose of this paper was to investigate experimentally the dependence of separation losses on bit density and head gap length, and to distinguish from the reading losses those losses introduced during the writing process. Briefly, results showed that, for the heads and tapes used in the experiment, virtually all the losses could be attributed to the reading process. Furthermore, writing with a wide gap head and reading back with the four heads established that the percentage reading losses as a function of separation were apparently the same whatever reading head was used. View full abstract»

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  • An investigation of high-frequency bias-induced tape noise

    Publication Year: 1965 , Page(s): 105 - 110
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    Bias-induced tape noise remains a major limitation of the SNR in audio magnetic tape recording systems. Defined as the increment in system noise incurred when the bias oscillator is turned on, the noise can originate from a number of different causes; namely, bias oscillator harmonic distortion, magnetized heads, the earth's magnetic field, and an intrinsic noise source. The latter noise source is our primary concern here. Such record system parameters as head-to-tape spacing, gap length, bias current, and bias frequency were investigated with regard to their influence on this intrinsic bias noise source. Two models of the mechanism of intrinsic bias noise are examined. The first, the "amplitude modulation model." proposes that bias noise is generated by amplitude modulation of the recorded bias signal by the physical and magnetic variations of the head-tape system. In this model, bias noise is merely the lower AM sidebands of the recorded bias signal. The second model relates bias noise to the interaction fields in erased tape. This model proposes that these fields behave similarly to normal recording fields and can be "re-recorded" on the tape at an enhanced level. The two proposed mechanisms are examined in the light of the experimental data. The amplitude modulation model is shown to agree with all the observed data with the exception of the existence of bias noise at bias wavelengths smaller than the particle size. The second model, which does not incorporate a wavelength dependency of bias noise, is in qualitative agreement with the observed data. Methods are discussed for reducing the bias noise without materially affecting the system performance. View full abstract»

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  • A magnetic feedback modulator for improved FM carrier recording

    Publication Year: 1965 , Page(s): 111 - 114
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    Magnetic multivibrators are often used as voltage-controlled oscillators in FM carrier recording systems. These oscillators generally consist of two switching transistors connected to a center tapped coil on a square loop magnetic core. The transistors operate alternately in saturation, driving the core between its positive and negative saturation limits. Frequency then depends upon saturation flux and applied voltage. In the Magnetic Feedback Modulator, stability and linearity improvement of an order of magnitude is possible with a new method of applying negative feedback to a square-loop core magnetic multivibrator. In addition, circuit complexity is reduced considerably over previous methods using conventional frequency detectors to derive feedback voltage. Based on Faraday's Law, a voltage which is a function of frequency and flux change is derived from the magnetic circuit. This voltage is then used as negative feedback to the dc differential amplifier to drive the magnetic multivibrator. Since the magnetic circuit is included in the negative feedback loop, frequency errors occurring in the modulator cause corresponding changes in the magnetic feedback voltage. The errors are then reduced in magnitude by the negative feedback. View full abstract»

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  • Some regulated power supply apparatus using the Morgan circuit

    Publication Year: 1965 , Page(s): 115 - 121
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    The SCR chopper circuit has a very wide range of application in regulating a dc power, and its merits are universally appreciated. Because of its merits, the circuit is most suitable for a nonfailure power source that supplies power from a set of rectifier-batteries to a communication equipment or any other electronic equipment, which requires a dc power source of several output voltages. For such purposes, the output voltage of the circuit should be smooth, accurately regulated, and should respond quickly; at the same time, the efficiency must be high and reliability excellent. This paper offers, firstly, some improvements on the Morgan circuit in order to make it peculiarly suitable for different kinds of practical applications; namely, the smoothing filter is made as small as possible to make the response of the circuit rapid, while the efficiency is kept high. Secondly, data, obtained through the analysis of the operation in the case of the small filter, are presented. Thirdly, the paper shows, as the result of such analysis, that if a saturable current transformer (SCT) is designed properly, the circuit will behave as a self-regulating constant voltage power source. Lastly, it proposes a practical application which has a suitable protecting circuit composed of some simple circuit elements providing against the failure of commutation which causes a severe overvoltage and overcurrent to the load. View full abstract»

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  • Magnetoresistive amplifiers with superconductive elements

    Publication Year: 1965 , Page(s): 122 - 126
    Cited by:  Papers (2)
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    The construction and properties of certain superconductive amplifiers in which the resistance of a gate element is controlled by the electromagnetic field of a signal coil are described in this paper. Vacuum-deposited films of tin, which have narrow resistive transition widths, have been used as the gate elements, and the field has been applied perpendicularly to the film surface. The parameters of small-signal analysis are determined, and the influence of temperature, bias magnetic field, and zero-signal gate current upon power gains are shown. The limitations and merits of the device in its present form are discussed. View full abstract»

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  • [Back cover]

    Publication Year: 1965 , Page(s): 0
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    Freely Available from IEEE
  • Eddy current loss in saturated solid magnetic plates, rods, and conductors

    Publication Year: 1965 , Page(s): 126 - 137
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1128 KB)  

    Included in this paper is a procedure which utilizes the digital computer to solve eddy current loss problems when the magnetization process extends into the nonlinear region of the magnetization curve. The values of permeability used in the equations are obtained from the actual magnetization curve, thus eliminating the approximations employed in most previous investigations. The nonlinear partial differential equations are replaced by finite difference equations and solved by numerical methods on an IBM 7070 digital computer. The investigation covers cases of both rectangular plates and cylindrical rods. For the cylindrical rods, cases involving piecewise homogeneous material as well as cases involving homogeneous material are considered. The material is said to be of a homogeneous nature, as the term is used here, when it satisfies the requirements that 1) resistivity be constant throughout the material; and 2) flux density and magnetic intensity be related by the same magnetization curve throughout the material. A cylindrical rod, composed of two concentric cylinders of different magnetic and electrical properties, is the piecewise homogeneous case covered in the present paper. Throughout the investigation, it is assumed that flux density and magnetic intensity are related by a single valued curve; hence, hysteresis effects are neglected. 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