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Magnetics, IEEE Transactions on

Issue 4 • Date July 1985

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Displaying Results 1 - 11 of 11
  • [Front cover and table of contents]

    Publication Year: 1985 , Page(s): 0
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  • Simulated annealing: An application in fine particle magnetism

    Publication Year: 1985 , Page(s): 1277 - 1282
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    Using a model of a system of interacting fine ferromagnetic particles, a computer simulation of the dynamical approach to local or global minima of the system is developed for two different schedules of the application of ac and dc magnetic fields. The process of optimization, i.e., the achievement of a global minimum, depends on the rate of reduction of the ac field and on the symmetry of the ac field cycles, The calculations carried out to illustrate these effects include remanence curves and the zero field remanence for both schedules under different conditions. The growth of the magnetization during these processes was studied, and the interaction energy was calculated to best illustrate the optimization. View full abstract»

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  • An improved measurement of the absolute efficiency of magnetic heads by saturating the gap field

    Publication Year: 1985 , Page(s): 1283 - 1288
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A method that can be used to measure the absolute efficiency of narrow-track magnetic heads such as video heads (gap area <103(μm)2) is described. The method is based on the detection of the gap flux by means of a subsidiary coil wound around the gap. Usually a considerable amount of leakage flux is detected together with the gap flux, which obviously would impair the accuracy of the results. Therefore, measures were taken by raising the current through the main coil progressively and thus determining the saturation value of the gap flux. In this way it was possible to distinguish between the gap flux and leakage flux components. With this method the efficiency can be measured with an accuracy of better than 10 percent at frequencies of up to 10 MHz. As a second result, the gap area can thus be determined magnetically as well. A comparison of the magnetic and optical gap area offers a check on the reliability of the efficiency measurement. The merits of this measuring method are discussed with the aid of results obtained for a typical ferrite video head. View full abstract»

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  • Characteristics of ideal probe heads with ideal windings in the presence of a permeable media underlayer

    Publication Year: 1985 , Page(s): 1289 - 1294
    Cited by:  Papers (2)
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    An analytical expression has been derived for the field of a two-dimensional infinitesimally thin probe head with the winding located at a finite distance from the probe tip. The results of the calculations presented illustrate the effect of the location of the winding on the fields of head models and their aperture functions. View full abstract»

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  • Temperature dependence of the effective permeability of heat treated Sendust alloys

    Publication Year: 1985 , Page(s): 1295 - 1300
    Cited by:  Papers (1)
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    The temperature dependence (-10°C-70°C) of the effective permeability (μeff) of Sendust alloys (Fe-9-10 wt% Si-5-7 wt% Al) quenched at a room temperature from the various temperatures (400°C-700°C) was investigated at every 2°C in the temperature range of -10°C to 70°C. Most of the studied alloys gave a peak of μeffin the studied temperature range. The peak temperature (Tp) giving the peak μeffvaried with different alloy composition. The alloys of Tp = 20°C are supposed to correspond to the alloys of the zero magnetocrystalline anisotropy constant (K1= 0) at 20°C. The deduced K1= 0 lines at various temperatures (-10°C-50°C) were obtained for an Fe-Si-Al ternary system. The values of peak μeffat the same Tp were different, depending on alloy composition, This difference is due to the difference in the polycrystalline magnetostriction constant (λ s) of the alloys. The peak temperatures of the studied alloys vary with the different heat treatments. This variation is due to the variation of K1, induced by the change in microstructures of the alloys. The variation of the values of peak μeffwith heat treatments was small compared to the difference of those in the alloys of different composition. It seems that the variation of the λ s with heat treatments would be small. Both the compositional dependence of μeffat 20°C and the temperature sensitivity (Δμeff/ΔT) were obtained for both the alloys cooled continuously to room temperature and those quenched at room temperature from 400°C. View full abstract»

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  • Annealing kinetics of thin permalloy films

    Publication Year: 1985 , Page(s): 1301 - 1305
    Cited by:  Papers (3)
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    Low-temperature (250-397°C) annealing was found to cause a large decrease in the resistivity of radio-frequency sputter-deposited thin (≤ 500 Å) Permalloy films. A transmission electron microscope was used to investigate a probable microstructural change occurring during the annealing. It was found that the low-temperature annealing induced considerable grain growth in these films. Furthermore, an electron diffraction analysis has shown that this grain growth was accompanied by the formation of the ordered phase (Ni3Fe). The use of dark-field imaging revealed that the small ordered region appears to be formed around the disordered regions via a grain-boundary diffusion mechanism. The observed resistivity decrease was proposed to occur by the structural ordering as a result of the annealing. The measured activation energy for this process was 0.72 eV. This activation energy appears to be associated with the grain boundary migration of excess vacancies trapped during film formation. View full abstract»

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  • Magnetic properties in the system Iron-Cobalt-Aluminum

    Publication Year: 1985 , Page(s): 1306 - 1309
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    The ternary alloy system Fe-Co-Al is studied in the body-centered cubic (bcc) phase for the composition dependence of room temperature magnetization, saturation induction, and Curie temperature Tc. The system has potential for high temperature application as soft magnetic material. The results expand upon earlier measurements. The presence of a broad maximum in magnetization near the composition 70 Fe-30 Co (weight percent) in their binary does not persist beyond about 5 wt% Al in the ternary family. Previously reported Curie temperature results are confirmed including an anomalous increase of Tcwith Al dilution for a certain range of composition. This feature is explained as due to a stabilization of the α-phase to higher temperatures. View full abstract»

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  • Analysis of tubular linear induction motors, using the concept of surface impedance

    Publication Year: 1985 , Page(s): 1310 - 1313
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    By using the surface-impedance method, equivalent circuit for an axial-flux tubular induction motor is obtained. This circuit is used to determine the performance characteristics of a laboratory model. The calculated results are compared with experimental results. The voltages and currents in the equivalent circuit are related directly to the field quantities within the actual device. View full abstract»

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  • The effect of stress on the magnetization of mild steel at moderate field strengths

    Publication Year: 1985 , Page(s): 1314 - 1320
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    Measurements are presented of the magnetization of mild steel, at field strengths between 100 A/m and 1200 A/m, for hysteretic and anhysteretic conditions. Magnetization was parallel or perpendicular to an applied uniaxial stress. The experimental results showed that tension parallel to the field or compression perpendicular to the field had relatively little effect on the flux density, but parallel compression or perpendicular tension reduced the flux density considerably. The theory presented predicts this symmetry, but it cannot account for other features of the measurements. View full abstract»

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  • "Iron-Deficient" YIG?

    Publication Year: 1985 , Page(s): 1321
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    In a recent letter to this TRANSACTIONS [1], Guyot, Cagan, and Merceron claim to have measured the initial permeabilities, at different constant temperatures, as a function of frequency, of "iron-deficient" yttrium iron garnet (YIG). They attribute the nature of their results to the presence of Fe4+ions in their samples, which provide a means of valency interaction. The method of preparation of the polycrystalline material on which these measurements were made is given in another letter [2] by the same authors. This author wishes to point out that this method, taken at face value, will not produce the material they claim. In fact, it is very unlikely that an "iron-deficient" YIG, which might be written Y3Fe5-δO12, with measurable δ, can be produced at all. View full abstract»

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  • [Back cover]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE

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