By Topic

Magnetics, IEEE Transactions on

Issue 5 • Date Sept. 1990

Filter Results

Displaying Results 1 - 25 of 505
  • 1990 International Magnetics Conference. INTERMAG

    Save to Project icon | Request Permissions | PDF file iconPDF (1998 KB)  
    Freely Available from IEEE
  • A new dual gate design for low current pulse operation in 16 Mb ion-implanted bubble memory devices

    Page(s): 2514 - 2516
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    A design for a dual gate which has both pseudoswap and block-replicate functions for 16-Mb ion-implanted bubble memory devices has been proposed and shown by Sato et al. (1987) to reduce the operation current-pulse amplitude. The dual gate is composed of a pair of hair-pin conductor patterns in two layers and ion-implanted tracks for the major line and the minor loop corner. The current pulses are applied through the hair-pin conductor patterns to stretch, cut, or annihilate bubbles for the operation of the dual gate. The functions of the dual gate were realized with low current pulses of less than 150 mA using 0.8-μm-diameter bubbles. It is therefore confirmed that the dual gate with low-current operation makes the 16-Mb ion-implanted bubble memory devices more practical View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An equilibrium analysis of helically symmetries plasmas using boundary element method

    Page(s): 1774 - 1776
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    The authors present a computational scheme based on boundary-element methods for analyzing helically symmetric equilibrium configurations which are described by the MHD (magnetohydrodynamic) equilibrium equation. To solve the equation numerically, a boundary integral equation is introduced. The authors describe an effective scheme for calculating the principal solution to the equation which includes an infinite series of slow convergence. The vacuum fields enclosed by a helical perfectly conduction shell are calculated on the basis of this scheme. It is shown that the shifts of magnetic surfaces decrease with the helical pitch or the displacement of the helical shell View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Substituted ferrite-garnet films with a GGG-CaMgZr substrate [210]

    Page(s): 2780 - 2782
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The possibility of increasing the DW (domain wall) velocity in high-Bi-content films was assessed experimentally. Bi-Pr-Lu-substituted garnet films with a GGG-CaMgZr substrate (210) which show very high DW velocities for a relatively low driving field and a high magnetooptical parameter were obtained. In these films, rhombic anisotropy is chiefly of the growth type, and variations of magnetic properties with temperature make these films promising media in fast magnetooptical devices View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Calculations of potential distributions produced by implanted electrodes in a man model by finite elements

    Page(s): 1777 - 1779
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The finite-element (FE) method is used to analyze and determine the potential distribution produced by implanted stimulating electrodes used in conjunction with an implanted defibrillator. These electrodes are used to deliver an energy shock to halt ventricular fibrillation during fatal arrhythmias in human beings. The FE solution was obtained by solving the Laplace equation using a Galerkin procedure. An infinite cylindrical model having three coaxial layers of tissue with two electrodes was used to show preliminary results of the FE model. An analytical procedure was developed and used to validate the FE results. The overall objective of this study is to develop a computer model for the study of defibrillation fields. This model can be used to estimate the potential distribution and potential gradients on the heart for various electrode sizes and configurations for a given shock strength. The most promising variation of these defibrillation-electrode configurations can be chosen for experimental testing in laboratory animals and possibly in human beings View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Error rate performance of experimental gigabit per square inch recording components

    Page(s): 2298 - 2302
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The authors measured the ontrack and offtrack error-rate performance of several combinations of experimental heads and disks using a partial-response channel at approximately 1 Gb/in2. The system components include a magnetoresistive head, a thin-film disk, and the partial response readback channel. Precompensation and equalization were used to tune the channel for best performance. Results indicate that these components can write and read data at 1 Gb/in2 with good error rates and offtrack margins View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Serpentine magnetoresistive elements for tactile sensor applications

    Page(s): 2047 - 2049
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Performance data on a new tactile sensor configuration are presented. The sensor is based on magnetoresistive (MR) technology but incorporates a patented serpentine path element structure which offers a wide range of advantages over previously considered designs. Previous work on MR tactile sensors did not approach the problem of sensor optimization at the transducer level. By placing the emphasis on the bottom-up method of design, a wide range of sensors for different applications could be developed. Sensitivity is a key feature in tactile sensor design. This is a measure of the minimum detectable force change that can be accurately detected. The requirement for high signal-to-noise ratios indicates the need for high element resistances, the use of AC magnetic fields, and small geometric size (pixel resolution) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An optimal formulation for 3D moving conductor eddy current problems with smooth rotors

    Page(s): 2359 - 2363
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    A finite-element technique for modeling 3D transient eddy currents in smooth-rotor conductors moving at a constant velocity is described. The method does not require the electric scalar potential inside conducting regions in moving-conductor problems. The interface between moving and stationary conductors requires a jump in magnetic vector potential when the electric scalar is not present. This is handled using a thin-surface element. The method has been implemented in the MEGA software package for modeling 2D and 3D electromagnetic fields. Eddy-current regions are modeled using a magnetic vector potential. Nonconducting regions require magnetic scalar potentials. Validation by comparison with experiment has been carried out. The study of eddy currents in an electromagnetic launcher is considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A vector moving model of non-aligned particulate media

    Page(s): 2116 - 2118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Attention is given to a vector moving model which computes the total magnetization of a medium by convolving a material-dependence scalar Preisach function, P, with a process-dependent vector, D. This vector is sensitive to the average orientation and switching characteristics of particles constituting the medium, and determines the overall direction of the magnetization. The Preisach function, on the other hand, determines the magnitude of the moment attached to each D. Media composed of particles with uniaxial anisotropy, which are dispersed in planes parallel to one another, are considered. The particles are symmetrically dispersed about the Preisach measurement axis, and all magnetic quantities of interest are two-dimensional within these planes. Characteristic switching of particles by the Stoner-Wohlfarth coherent rotation and by more general incoherent modes is considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transverse magnetical stress of rapidly quenched NdFeB-ribbons

    Page(s): 2598 - 2600
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    The authors investigated the transverse magnetic stress (TMS) of rapidly quenched NdFeB by measuring the θ-remanence for 0<θ⩽180°, where θ is the angle between the direction of the applied field during the measurement and the direction of the previous magnetization. Through TMS the remanence was spread out over a wide field range, H≈0 to H>2750 kA/m. This result can be explained by interaction fields, where positive and negative interaction fields of more than 1000 kA/m must be assumed. It is suggested that the discrepancy between the 180° remanence and the 90° remanence is due to the magnetic hardness of the grains, which depends on the projection of the magnetizing field on the easy axis of the grain View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Observation and simulation of 0.3 μm length domain on a high speed rotating magneto-optical disk

    Page(s): 1912 - 1914
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    The magnetooptical recording characteristics of a 0.2-0.3-μm-length domain were studied using a magnetic field modulation method. The ultimate goal of the investigation, performed on an extremely high-density magnetooptical disk, was to realize high-speed rotating 5.25-in disks. Through optical observation, it was found that domains of 0.3-μm length could be recorded separately under the condition of 15.1 m/s linear velocity and 25.2 MHz. However, the domain shape became more irregular with increasing recording power and linear velocity. This could be explained by calculated results showing that the domain wall temperature when the magnetic field is reversed becomes higher as the power or the velocity increases. It was observed that the domain shape of a quadri-layer structure disk with a reflective layer having a higher thermal conductivity, such as Al film, is more irregular. This is explained by the difference in temperature profiles obtained from simulation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structure and magnetic properties of Co-based multilayers

    Page(s): 2733 - 2735
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The structure of Co/Cr and Co/W magnetic multilayers has been characterized by high-resolution electron microscopy and correlated with the magnetic properties determined using a vibrating sample magnetometer. It is shown that the layer thickness, crystal texture, and degree of interfacial mixing effect the magnetic properties. Mixing at the interfaces has been observed, resulting in a reduction of the Co able to contribute to the magnetization of the magnetic multilayer films View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Waveguide analysis of multisectional magneto-optical isolator

    Page(s): 2783 - 2785
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    A wave optics analysis of light propagation in a multisectional magnetooptical waveguide isolator is performed. The action of the whole element can be mathematically described as the multiplying of complex matrices. Specifically, a simple stepwise isolator design with input TE (transverse electric) polarization is analyzed. The dependence of the output TM (transverse magnetic) power on the length of one full sector is computed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A design of high performance inline head assembly for high-speed access

    Page(s): 2445 - 2447
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A high-performance inline head assembly that stabilizes head sliders during high-speed access has been developed. It features a triangular, truss-bridge-shaped load beam and a flexure supported at both ends by the load beam. These improvements made the resonant frequency in the access direction twice that of the conventional inline head assembly, reducing spacing fluctuation at high frequencies and allowing the actuator to be positioned more precisely. The proturberance was moved to the load beam from the flexure, lowering the moment by decreasing the distance between where the force was applied to the slider and the slider's center of gravity. Experiments showed that the resonant frequency of the inline head assembly is 8 kHz in the access direction, which is about twice that of the conventional inline head assembly. Spacing fluctuation is about 50% that of the conventional inline head assembly View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Passage of surface magnetostatic waves through magnetic `valley' and `ridge'

    Page(s): 1480 - 1482
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    The propagation of magnetostatic surface waves (MSSWs) in a ferrite film magnetized by a nonuniform magnetic bias field in the shape of a magnetic valley or a magnetic ridge has been investigated theoretically and experimentally. The MSSW beam paths and the beam profiles have been studied at different frequencies for different angles of orientation of the input MSSW transducer relative to the direction of the bias magnetic field. It is noted that the results obtained can aid in the construction of microwave MSSW devices with nonuniform bias fields View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Heat treatment effects of CoCr sputtered films

    Page(s): 1623 - 1625
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    Thermomagnetic analyses of RF-sputtered Co84Cr16 and Co78Cr22 thin films are reported. It is found that, when CoCr film is heated lower than the HCP→FCC transformation temperature, Ms drops substantially after holding at a constant temperature, and Ms at room temperature decreases after one cycle of heat treatment. This is due to Cr redistribution from the Cr-rich region of the film. When CoCr is heated higher than the HCP→FCC transformation temperature, M s jumps sharply after holding at a constant temperature. This is due to the formation of an FCC phase with high Ms at higher temperature. A study of the angular dependence of coercivity indicates that the demagnetization mechanism of as-sputtered film seems to be an incoherent rotation mechanism while for the heat-treated film it may be domain wall motion or another combined mechanism. The perpendicular anisotropy in the Cr film may be connected with the existence of a highly Cr segregated region as well as c-axis alignments View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the performance and implementation of a class of error and erasure control (d,k) block codes

    Page(s): 2312 - 2314
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    The error performance and implementation of a class of error- and erasure-correcting (d,k) block codes are investigated. These codes can be represented by restricted integer compositions of arbitrary length, appended with a small and fixed number of redundant bits. Bounds on block-error rates and error-probability curves obtained by simulations are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A theoretical comparison of detection techniques on R-DAT

    Page(s): 2157 - 2159
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    Two alternative detection techniques are simulated on a model of a R-DAT recording channel. The R-DAT model includes electronic and head noise, media noise, adjacent track interference, and overwrite interference. By using this model, the two alternative detection techniques (Class IV partial response and a compromise DC Viterbi detector) are compared with reference flat equalization. Both techniques show some advantage in signal-to-noise ratio margin View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coercivity control of RF magnetron sputtered CoCr films by external magnetic field

    Page(s): 1617 - 1619
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    CoCr films were prepared on glass substrates with uniform magnetic fields applied perpendicular to the substrate surface. When the magnetic field was varied from 0 to 96 Oe, the perpendicular coercivity of 20 at.% CrCo films made at an Ar pressure of 1.5 mtorr increased from about 100 to 850 Oe. The c-axis dispersion slightly increased by about a degree. At a magnetic field of 96 Oe, a lower Ar pressure of 1 mtorr resulted in a higher coercivity of 1000 Oe. X-ray analysis revealed a correlation between the coercivity and the microstrain as well as lattice coherency View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A post-compensation scheme for peak-detect channel

    Page(s): 2303 - 2305
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    A postcompensation procedure for peak detection in disk-drive systems has been tested using a software channel on (2,7) RLL (run-length limited) codes. It uses a table lookup method to determine the detection-window boundaries for the center pulse in every three-pulse sequence. Preliminary test results against read-back equalization schemes suggest that the procedure may perform better than equalization techniques in terms of the ability to reduce the soft error rate. The technique does not boost the noise components of the read-back signal and thus may provide better phase-error reduction than read-back pulse-slimming equalization techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Computation of 2D and 3D eddy currents in moving conductors of electromagnetic retarders

    Page(s): 2382 - 2384
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    The AV-A formulation is applied to problems where motion is the source of eddy currents. The Lorentz gauge is used to ensure uniqueness of the solution and leads to a two-step computation procedure: A is computed first, followed by V on moving regions only. A stable and accurate solution of A is obtained through implementation of a Petrov-Galerkin method. Numerical results of 2D and 3D problems are included View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transient 3D eddy current calculations in fusion reactors

    Page(s): 2364 - 2366
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The transient discharge behavior of a large superconducting coil in a vacuum vessel which is part of the TOSKA test facility is studied. Several rates of change in the magnetic field are simulated by assuming the current of the coil to decay exponentially with different time constants. The eddy-current field in the metallic parts is computed by means of various vector-potential formulations. The merits and disadvantages of the different methods are discussed. The implications of the resultant forces and losses for the design of this fusion experiment are identified View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Calculation of the size dependence of the coercive force in fine particles

    Page(s): 2119 - 2121
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    A numerical micromagnetic model is employed to calculate the energy barrier for the reversal in a γFe2O3 particle of cubic shape. The model simulates magnetization reversal by coherent rotation and curling. It simulates the thermal fluctuations of the magnetization by a method or parametric optimization and gives the dependence of the coercive force on particle size. The size dependence of the switching field is a good qualitative fit to experimental data. A small reduction in the superparamagnetic size of γFe2O 3 particles is attributed to the surface imperfection. The flower magnetization configuration appears to be metastable over an intermediate size region, and a spontaneous transition to a vortex state of lower energy is expected at normal temperatures View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New method of making Nd-Fe-Co-B full dense magnet

    Page(s): 2601 - 2603
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    A novel method for fabricating an isotropic fully dense Nd-Fe-Co-B magnet is described. This method consists of a plasma-activating process and a hot-pressing process. The magnetic powder is heated by resistance heating. Plasma activation produces an improvement in the Hcj of the compacted magnet. The pressure range is from greater than 200 kg/cm2 to less than 500 kg/cm2 . Optimum alloy composition is Nd13.5Co1.5B 6Fe64.5, specified by magnetic properties and formability in hot pressing. The magnetic properties of this magnet are 15 MG-Oe for BHmax and 17 kOe for Hcj . The temperature coefficient of Br is -0.07 to -0.08%/°C, and that of Hcj is -0.39 to -0.42%/°C View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Incident angle dependence of recording characteristics of vacuum deposited Co-Cr films

    Page(s): 2286 - 2288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The authors report on an investigation of the relation between the incidence angle of evaporated atoms onto a substrate and the magnetic properties, microstructure, and recording characteristics of Co-Cr films. The Co-Cr films deposited at an oblique incidence angle have an easy axis of magnetization which tilts from the film normal and consist of columnar grains which tilt from the film normal. For films deposited at an incidence angle from 55° to 20°, the isolated pulse waveform is not a double pulse, but a single-peak-like pulse with narrow pulse width. An eye pattern for moving-picture digital recording was clearly observed using the Co-Cr tapes. The compensation amplitude in the short wavelength region was very small, and equalization such as a Hilbert transform was unnecessary for films deposited at an incidence angle from 55° to 20 ° View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

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