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Magnetics, IEEE Transactions on

Issue 3 • Date May 1980

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Displaying Results 1 - 16 of 16
  • [Front cover and table of contents]

    Page(s): 0
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  • Effect of conductor crossings on propagation margins

    Page(s): 489 - 497
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    The effects of conductor delineation technique on magnetic bubble propagation across the conductor edge are described. Propagation margins are obtained for bubble circulation around 18-μm diameter Permalloy discs which cross four edges of an Al-Cu feature. Specifically investigated are isotropic wet etching, anisottopic wet etching to achieve a uniform taper, ion beam milling, and metal lift-off to provide a planar structure. Margins are obtained at ± 40°C, with the most significant degradation observed at the lower temperature. Permalloy magnetic continuity in the crossings can be inferred from hysteresis loop measurements of a Permalloy sheet deposited over a grating pattern formed by the above processing techniques. Although the least anisotropic loops are invariably obtained with smoothly tapered Al-Cu edges under the Permalloy, propagation margins are not maximized with such structures, but rather favor a planar crossing. The results suggest that although patterned stress is still an important concern in functional operation, other geometric effects can be more significant. In particular, poor magnetic step coverage as inferred from loop measurements leads to spurious pole formation from the drive field, while even with adequate step coverage, static bias-field distortions can result because of the component of the field along the step. View full abstract»

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  • Complementary permalloy bubble propagation structure

    Page(s): 497 - 501
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    Field-access bubble propagation has been achieved in a novel Permalloy structure made up of a pattern and its complement. The pattern is defined by a step in a nonmagnetic spacer on top of which the Permalloy is deposited leaving the Permalloy in two levels. The two layers act in concert to provide coherently travelling potential wells for bubble propagation. The stepped structure is fabricated using a lift-off technique (4000-6000 Å) of Schott glass. Permalloy (1500-2500 Å) is then deposited by radio frequency sputtering over the entire device area. Devices of 10-μm period and 2- to 3-μm minimum feature were fabricated on 2-μm bubble garnets. A propagation margin >10 percent was obtained for 35-to 50-Oe drive fields. View full abstract»

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  • Wavelength response of harmonic distortion in AC-bias recording

    Page(s): 501 - 506
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    Wavelength response of harmonic distortion in ac-bias recording is analyzed. The wavelength response is affected in both the record and playback processes. In the record process tape nonlinearity and magnetization phase shift, which is dependent on signal-field intensity, are taken into account. In the playback process, tape thickness, tape-to-head spacing, gap length, etc. axe taken into account. An approximate expression for the third-harmonic distortion is derived. The experimental data show quantitative agreement with theory. View full abstract»

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  • Statistical analysis of signal and noise in magnetic recording

    Page(s): 507 - 513
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    A general theory is developed for the power spectrum of the induced voltage at the read head in magnetic recording, originating from the particulate nature of the tape. The theory is general in that it yields the signal power as well as the noise spectrum, including the effects of clustered particulate media. The statistics of all relevant parameters such as particle length, particle magnetic moment, and partial penetration of the signal into the layer have been taken into account. Experiments on nonoriented Fe2O3showed a discrepancy at short wavelengths of the order of 10 dB. This is qualitatively explained by particle interaction mechanisms. View full abstract»

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  • Fatigue softening and hardening in mild steel detected from Barkhausen noise

    Page(s): 514 - 517
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    The measurement of Barkhausen noise is used to follow the fatigue process in a mild steel. The variation in the root-mean-square (rms) value of the noise with bending stress during single-strain cycles and in unloaded samples is determined at several stages of fatigue life. The fatigue softening and hardening are found to be sensitively revealed by specific changes in the shape and area of the noise versus stress loops and also in the variation in the noise in unloaded samples, corresponding to changes in the residual stress state. The high sensitivity of the magnetic measurement technique is emphasized. View full abstract»

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  • Magnetic properties of 6.5-percent Si-Fe filament formed by a modified taylor technique

    Page(s): 517 - 520
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    A modified Taylor technique for forming 6.5-percent Si-Fe filament has been developed. The filament is much more ductile than the bulk 6.5-percent Si-Fe alloy and can be formed into wound cores easily. High permeability is maintained for frequencies up to 100 kHz for filaments with diameters of less than 100 μm. This material could be used in high-frequency magnetic cores. View full abstract»

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  • The Fe-B-C ternary amorphous alloys

    Page(s): 521 - 525
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    The properties of amorphous Fe-B-C alloys have been studied. The replacement of boron by carbon reduces the thermal stability of alloys containing more than approximately 80-percent iron, increases the Curie temperature slightly, and decreases the slope of the magnetization-temperature curve. Thus, although the low-temperature saturation magnetization decreases on replacement of B by C, as expected, the room-temperature magnetization exhibits a broad ridge of constant saturation magnetization per gram extending from approximately Fe80B20to approximately Fe83B11C6. This ridge follows one of the low-temperature magnetization contours. The density of the alloys in the series Fe84B16-xCxwas measured and compared to calculated densities. The increase in density agrees with the calculated values and results in a slight increase in saturation magnetization per unit volume with increase in carbon. The coercivity, both as-cast and after stress relief annealing, increases on replacement of B by C. This is not understood. View full abstract»

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  • Low-cobalt Cr-Co-Fe magnet alloys obtained by slow cooling under magnetic field

    Page(s): 526 - 529
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    The permanent magnet properties of magnetic field aged Cr-Co-Fe alloys containing 5-9 weight percent (wt %) Co were investigated. By slow cooling from above the spinodal temperature under applied magnetic field, energy products of (BH)max= 4-6 MG . Oe were obtained. The effects of cobalt content, cooling rate, and applied magnetic field strength were studied. View full abstract»

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  • Further studies of the miscibility gap in an Fe-Cr-Co permanent magnet system

    Page(s): 529 - 533
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    The miscibility gap of an Fe-Cr-Co system is further examined by monitoring the microstructures and the magnetic properties of the alloys. It is shown that the shape of the miscibility gap is not parabolic but of a peculiar shape, protruding to the Fe side along the Curie temperature. The part of the protrusion of the miscibility gap is called the "ridge" because of its shape resemblance. It is demonstrated that the alloys in the ridge region can exhibit very good magnetic properties. An Fe-25%Cr-12%Co alloy gives the magnetic properties asBr = 1.45T(14.5 kG),bHc = 50.1kA/m (630 Oe) and (BH)max = 61.3 kJ/m3(7.7 MG . Oe), which are almost comparable to those of the columnar Alnico 5 magnets. View full abstract»

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  • Transformation kinetics of the ferromagnetic alloy Mn-Al-C

    Page(s): 534 - 536
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    Mn1-x-yAlxCyforms a ferromagnetic metastable tetragonal τ-phase in the composition range0.42 leq x leq 0.47and0 leq y leq 0.021. Its high unaxial magnetocrystalline anisotropy makes it an interesting candidate for a permanent magnet. In order to investigate the kinetics of the transformations which occur in this system, we established the time-temperature-transformation diagram of a ternary alloy with the composition Mn0.538Al0.446C0.016. It was homogenized for 2 h at 1375 K, quenched, and subsequently isothermally annealed at temperatures between 625 K and 1025 K for various times ranging from one minute up to seven days. The quantitative phase analyses were performed by means of x-ray diffraction and stereological analysis of the microstructures. The addition of carbon increases the stability of the τ-phase, thereby allowing longer annealing times for the formation of single-phase samples. View full abstract»

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  • Magnetostrictive properties of rare earth-iron Laves phase materials prepared by powder metallurgy techniques

    Page(s): 536 - 540
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    A powder metallurgical approach has been utilized for preparation of highly magnetostrictive rare earth-iron Laves phase compounds. The results of dilatometric studies indicate that the liquid-phase sintering kinetics are in reasonable agreement with the concept of a phase boundary reaction as the rate-limiting factor. Magnetic powder orientation prior to sintering is found to improve magnetostriction of these compounds substantially. View full abstract»

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  • The spatial distribution of flux waveform across the limbs in a three-phase transformer core

    Page(s): 540 - 544
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    A scale model of three-phase three-limbed transformer cores, in which the magnetic path length varied significantly within the width of the limbs, was instrumented to observe the flux distribution in the laminations. Across the width of the center limb the local field was found to decrease monotonically with distance from the window and was minimum at the middle of the limb. In the outside limbs the local field was maximum near the window and gradually decreased across the width. The harmonic components varied in a similar fashion, although those in the center limb were 65 percent higher than those in the outside limbs. The experimental results confirmed that the magnetic material locally traverses a characteristic hysteresis loop. View full abstract»

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  • FFT calculation of magnetic fields in air coils

    Page(s): 545 - 549
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    The magnetostatic field produced by an air coil that possesses one-dimensional periodicity can be expressed as a one-dimensional discrete convolution of two functions. The first function expresses the field produced by a single turn of the coil. The second is a shape function; it expresses the spatial position and strength of current of each turn of the coil. The discrete convolution of these two functions gives the magnetostatic field produced by the coil. This paper presents one application of linear system theory to an air coil calculation, the use of the fast Fourier transform (FFT) in computing magnetostatic magnetic fields from air coils. A program is described which uses FFT convolution to perform this calculation. View full abstract»

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  • [Back cover]

    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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Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology