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Magnetics, IEEE Transactions on

Issue 2 • Date June 1969

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Displaying Results 1 - 15 of 15
  • [Front cover and table of contents]

    Publication Year: 1969 , Page(s): 0
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    Freely Available from IEEE
  • A survey of some physical limitations on computer elements

    Publication Year: 1969 , Page(s): 82 - 90
    Cited by:  Papers (4)
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    Some limitations imposed on the basic attributes of computer elements that arise from physical law rather than from consideration of technology or cost are surveyed in the light of recent literature. In particular, discussions are given of the reliability of storage of information, of the physical size, and of the speed of response of elements of the memory of a large, high-speed, digital computer. The various factors affecting the reliability considered include: logical and physical redundancy, crosstalk and the resulting difficulties of single-particle memory elements; storage lifetime in a nonequilibrium (steady-state) device is also discussed. The limits on size of semiconductor devices include: the minimum size of the voltage pulse needed for nonlinear operation, the limitations set by the need for cooling, by fluctuations in impurity content, and by the resolving power of fabrication processes. The effects of the inertia of matter on the speed of operation are discussed generally, noting the different magnitudes of response of transitions involving electronic rearrangements as compared to spin rotations or nuclear motions. Finally, comments are made on the possibility in principle of ultradense packing because of the extreme smallness of the atomic scale, and on the biological examples of such ultradense packing that exist in the genetic code and the mammalian brain. View full abstract»

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  • A theoretical limit to digital pulse resolution in saturation recording

    Publication Year: 1969 , Page(s): 91 - 97
    Cited by:  Papers (1)
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    A consistent method of calculating the single transition output voltage pulse shape of maximum resolution is derived. It follows (in a single mathematical step) both components of the magnetization through the demagnetization, remagnetization, flux collection, and differentiation processes appropriate to magnetic head readout. The single mathematical step is that of finding the Fourier transform of the equivalent of the tape-reproduce head transfer function. Such functions have been published previously. In a limiting case the transform is shown to yield the expected simple result. In general, the transform can only be evaluated numerically and this reflects the extreme complexity of the processes involved. Several graphs are shown of computed pulses and finally an appendix gives the peak amplitude 50- and 20-percent half-widths of computed pulses appropriate to a wide range of parameters. View full abstract»

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  • Magnetostrictive offset and noise in flux gate magnetometers

    Publication Year: 1969 , Page(s): 98 - 105
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    Longitudinal magnetostriction of the core material is found to be the principal source of offset and noise in present state-of-the-art flux gate magnetometers. Magnetostrictive offset is identified with even harmonics of the steady-state induced EMF resulting from the periodic elongation (or contraction) of the core material. Magnetostrictive noise is identified with random fluctuations of the magnetostrictive offset caused by frictional forces exceeding the magnetostrictive stress when the core material is near zero elongation. An analytical model and experimental results of magnetostrictive offset and noise are presented. It is expected that flux gate magnetometers with zero magnetostriction of the core material will yield a significant increase in signal-to-noise ratio with corresponding decreases in offset and magnetomotive drive power. View full abstract»

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  • Influence of the substrate and electrolyte on the composition and properties of thin electrodeposited Ni-Fe films

    Publication Year: 1969 , Page(s): 106 - 111
    Cited by:  Papers (3)
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    The characteristics of electrolytes will be described which prevent composition gradients from developing as the result of differences in Ni++ and Fe++ diffusion, during the electrolytic formation of Ni-Fe films. This is accomplished by using an electrolyte additive which results in a solution which can be operated at a Ni-Fe ratio that is the same as desired in the film, making both the Ni++ and Fe++ deposition diffusion controlled. Using a specific electrolyte with these characteristics, the influence of the substrate on the film composition, structure, and resultant properties has been demonstrated by changing the composition gradients induced by electrolyte diffusion effects. The metallurgical structure (grain size, porosity, crystal texture, composition) and the magnetic properties ( H_{c}, H_{k}, \alpha _{q} , magnetostriction) of films deposited on Au and Cu were examined. Using the Au substrate, films were made at constant deposition conditions from 100 to 4000 Å thick. The average Fe content of the films changed from 28 to 18 percent over this thickness range. Films deposited under the same conditions onto Cu substrates had a lower average Fe content; e.g.,13 percent at 600 Å thick. Film compositions as a function of thickness are described by the sum of two exponential terms; one term takes into account electrolyte diffusion effects on composition and the other term takes into account the electrode effect on composition. Previously reported data are analyzed in the same manner and composition gradients as a function of film thickness are confirmed to be larger than in the work reported here. Low values of coercive force and dispersion were obtained only from films thicker than about 300 Å deposited on Au. These low coercive forces and dispersion are shown to be due to the isotropic crystal structure, fine grain size, and relatively mild composition fluctuations in the Ni-Fe promoted by the characteristics of the Au substrate in the electrolyte. On Cu the films were magnetically isotropic and high in Hcbelow thicknesses of about 4000 Å, due to the highly porous film structure and large grain size induced by the Cu substrate. The deposition potentials, monitored- during the formation of the film, reflected the composition of the alloy depositing and provides a technique for choosing the optimum substrate and electrolyte. View full abstract»

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  • The reduction of magnetism during the electrodeposition of thin permalloy films

    Publication Year: 1969 , Page(s): 112 - 114
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    The paper includes a new aspect on elimination of the composition gradient in electrodeposited magnetic thin films. By addition of cathodically reducible ions of antimony, selenium, or tellurium to the electrolyte, it is possible to incorporate these non-magnetic elements in the initially deposited film zones preferably. Because of the high amount of the nonmagnetic element these inhomogeneous zones of the ternary Permalloy film become non-magnetic and do not affect the homogeneous zones of the film used for storage purposes. Besides the examined systems Ni-Fe-Sb, Ni-Fe-Se and Ni-Fe-Te, some other ternary or quaternary systems given in a forecast may show this effect. Experimental conditions and data support the investigations. View full abstract»

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  • Magnetic properties and creep observations of Ni-Fe films 30 to 300 Å thick

    Publication Year: 1969 , Page(s): 115 - 118
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    Coercivity, induced uniaxial anisotropy field, angular dispersion, residual stress, magnetic domain wall, and magnetization creep of vapor-deposited 81.7 Ni-18.3 Fe films are reported. The thickness and temperature dependence of the coercivity and the induced uniaxial anisotropy field in the thickness range from 30 to 16 000 Å are described. A substrate temperature range is given for minimum residual stress. Lorentz micrographs of magnetic domain walls and magnetization creep of films in the thickness range from 30 to 300 Å are presented. It has been found that Néel walls creep under the influence of a unipolar hard-axis field pulse in the presence of a constant dc easy-axis field. The paper discusses the experimental results in the light of existing creep theories. View full abstract»

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  • Strain insensitive Ni-Co films over a wide composition range

    Publication Year: 1969 , Page(s): 119 - 122
    Cited by:  Papers (1)
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    The magnetic properties of vacuum deposited Ni-Co films have been studied as a function of film composition, film thickness, and substrate temperature. The experimental parameters ranged from 400-1000 Å for thickness 17-41-percent Ni for composition and room temperature to 300°C for the substrate temperature. It was found that the magnetoelastic strain coefficient approaches zero in the vicinity of 35-percent Ni in agreement with Tolman's result[1] and remains insensitive to film composition from 30-40- percent Ni. These results are in reasonably good agreement with calculations based on single crystal data and the expression of Callen and Goldberg [10]. The coercive force and anisotropy field are an order of magnitude larger than of nonmagnetostrictive Permalloy films. An unexpected result is an increased coercive field with increasing film thickness while the anisotropy field remains practically constant; the films become inverted at a critical thickness in the order of 750 Å For a wide variation of preparation parameters the crystallite size remained less than 100 Å View full abstract»

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  • A transmission line technique for measuring the properties of magnetic films

    Publication Year: 1969 , Page(s): 123 - 125
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    A novel technique is described to use the magnetic-loading effect of a film on a strip transmission line as a means for measuring the magnetic properties (anisotropy and coercivity) of a thin film. This technique is easy to implement and is particularly useful for film arrays where strip transmission lines are of sufficient length to permit a clear resolution of the film-loading effect. View full abstract»

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  • Thermal hysteresis in ferrite memory cores

    Publication Year: 1969 , Page(s): 125 - 132
    Cited by:  Papers (1)
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    The effects of different writing and reading temperatures on the switching voltage waveform, permeability, and flux state of standard nickel-copper-manganese and copper-manganese ferrite memory cores have been investigated over a temperature range of 0 to 70°C. These temperatures are well below the Curie temperatures of the materials being tested. It has been found that writing at a higher temperature than the read temperature leads to increased low temperature voltage switching thresholds, higher low frequency (<40 MHz) permeabilities, lower high frequency (>40 MHz) permeabilities, and flux states almost equal to the equilibrium value for the lower temperature. Read current pulse rise time and duration have been found to have no effect on the increase in threshold with temperature. Externally produced stresses have been used to simulate the effects of temperature changes on the core. View full abstract»

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  • Magnetoelastic wave propagation in single-crystal lithium ferrite

    Publication Year: 1969 , Page(s): 132 - 136
    Cited by:  Papers (1)
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    The time delay of a magnetoelastic wave traveling in a constant field gradient is obtained for a lossless ferrimagnet without the use of the small-coupling approximation. The theory is used to calculate the delay of microwave pulses in lithium ferrite and in yttrium iron garnet single crystals. Echoes delayed by magnetoelastic wave propagation in a rectangular bar of single-crystal lithium ferrite are reported. View full abstract»

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  • Forming structure and magnetic properties of Alnico VS55 alloys

    Publication Year: 1969 , Page(s): 136 - 139
    Cited by:  Papers (1)
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    Some results of explorations on crystallographic structure perfection of Alnico VS55 single crystals are presented. Segregation and block disorientation in crystals are shown to have some influence on the process of spinodal decomposition in a magnetic field, and on permanent magnet properties. View full abstract»

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  • Observation of rotational variations in plated wire memory elements

    Publication Year: 1969 , Page(s): 139 - 140
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    First Page of the Article
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  • [Back cover]

    Publication Year: 1969 , Page(s): 0
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    Freely Available from IEEE
  • On carrier-frequency gating systems for static switching circuits

    Publication Year: 1969 , Page(s): 140 - 142
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Carrier-frequency gating systems for exciting static electronic switches such as thyristors are examined. The effect of the commutation in the output rectifiers during transmission of the carrier wave is to cause an instantaneous drop in the output voltage during commutation. A compensation for the commutation drop by an overlap technique is proposed, and comparative experimental observations presented on two types of systems. 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