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Magnetics, IEEE Transactions on

Issue 6 • Date November 1982

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Displaying Results 1 - 25 of 253
  • [Front cover and table of contents]

    Publication Year: 1982 , Page(s): 0
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    Freely Available from IEEE
  • Preface

    Publication Year: 1982 , Page(s): 1048
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  • Application of the finite element method to the design of permanent magnets

    Publication Year: 1982 , Page(s): 1049 - 1051
    Cited by:  Papers (7)
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    A new method of determining the lengths of magnets in a magnetic circuit by using the finite element method has been developed. This method has the advantage that the lengths of magnets which produce the prescribed flux distribution can be directly calculated. In this paper, the error of this method is discussed at first, and then an example of application determining the shape of a magnet is shown. This method is effective for the design of magnetic circuits consisting of several permanent magnets and the determination of the shapes of magnets. View full abstract»

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  • Determination of winding inductances in ferrite type permanent magnet electric machinery by finite elements

    Publication Year: 1982 , Page(s): 1052 - 1054
    Cited by:  Papers (26)
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    A key design factor in ferrite type permanent magnet machines is the accurate knowledge of the values of machine winding inductances during the design stage. In the present paper, a method which is based on perturbation of the energy stored in the magnetic field, and on numerical models of simulation of such permanent magnets is used in calculating machine inductances. The effect of change in the values of these winding inductances with magnet position throughout the cycle of operation of such machines is given. These inductances also include the apparent and incremental values, whose definition is directly related to the choice of apparent or incremental reluctivities in the energy perturbation process. Results of application of this method to the calculation of inductances in a 15 hp 6-pole ferrite type electronically operated permanent magnet machine are given. These calculated values of inductances are in good agreement with the measured values. View full abstract»

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  • Magnetic performance of step-lap joints in distribution transformer cores

    Publication Year: 1982 , Page(s): 1055 - 1057
    Cited by:  Papers (11)
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    The magnetic characteristis of cores with step-lap joints are analyzed by using the finite element method taking into account eddy current and magnetic saturation. The effects of the following factors on the magnetic characteristics such as flux and eddy current distributions and magnetizing current are clarified quantitatively. 1)step-lap length 2)length of air gap at the joint 3)number of laminations per one stagger layer 4)flux density (magnetic saturation) Obtained results give useful suggestions improving the design of the joints of transformer cores. View full abstract»

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  • Electromagnetic field formulation for eddy current calculations in nondestructive testing systems

    Publication Year: 1982 , Page(s): 1058 - 1060
    Cited by:  Papers (8)
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    The authors present the most practical configuration for detecting cracks in material, by applying an electromagnetic field along the largest dimension of the crack. An electromagnetic field formulation of the system equation is proposed using Maxwell's relations and separating the magnetic field into externally applied field and reaction field. The system equation is solved by using two classical methods : finite element technic for spatial problem and finite difference for time discretisation. So two dimensional eddy currents can be calculated immediately and related to the excitation characteristics for impedance calculation. Eddy currents lines in material for different cracks and sensor positions are presented. Theoretical results show important impedance changes. View full abstract»

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  • BIE analysis of eddy current losses in rectangular busbars in nonuniform fields

    Publication Year: 1982 , Page(s): 1061 - 1063
    Cited by:  Papers (2)
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    This paper deals with the computation of the time harmonic eddy current losses in a long nonmagnetic bus-bar with a rectangular crosssection due to the proximity of the various components of the power system. A quasi three dimensional analysis is presented in which the bar is assumed infinitely long but the axial nonuniformity of the field is taken into consideration. Fourier integral is used to represent the field as a spectrum of axially travelling waves. The induced fields due to each wave are analyzed through a boundary integral equations formulation. Numerical results are presented for busbars connected to an air cored shunt reactor. Potential problems arising from these losses are indicated and simple design guides are given. View full abstract»

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  • Calculation of eddy current losses in air coils by finite element method

    Publication Year: 1982 , Page(s): 1064 - 1066
    Cited by:  Papers (12)
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    Calculations of eddy-current losses in air coils by Finite Element Method are described. For simplification the geometry of the problem is considered to be axisymmetric neglecting the pitch of turns. Therefore, each turn represents a separate conductor and the resulting multiconductor system is treated by the superposition principle. Since the number of calculations is directly related to the number of turns the solution becomes very time consuming even for large computers. To improve efficiency of the method a modified Frontal Solution algorithm has been developed providing the possibility of multiple solutions add, in addition, advantage was taken of the symmetry of the admittance coefficient matrix of the multiconductor system. For accuracy reasons quadratic and cubic isoparametric elements are used. For two reactors the eddy current behaviour was investigated and losses were calculated. The numerical results show excellent agreement with results obtained experimentally. View full abstract»

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  • Application of integral equations to the magnetic field analysis of rotating electrical machines

    Publication Year: 1982 , Page(s): 1067 - 1069
    Cited by:  Papers (1)
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    An integral equation (IE) method is applied to the magnetostatic field analysis of salient-pole synchronous machines. A brief description of the method and verification with a known analytical solution are given. The method requires discretization only in the steel regions and does not necessitate any special treatment of the boundary conditions. For a two dimensional solution, the machine cross section is discretized into small triangular elements over which the magnetization can effectively be assumed constant. The resulting nonlinear algebraic equations are solved using the Gauss-Seidel iterative procedure. Application of Ampere's circuital law around the current carrying regions, combined with overrelaxation, is used to speed convergence. An open circuit analysis is performed on a synchronous motor, where, because of the field symmetry, only one half pole pitch need be discretized. The resulting open-circuit voltage characteristic shows very good agreement with the test curve. View full abstract»

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  • Interactive modelling of magnetisation curves

    Publication Year: 1982 , Page(s): 1070 - 1072
    Cited by:  Papers (2)
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    Programs are described which act as data base manager and editor for libraries of magnetic material descriptions in computer aided design. Curves are modelled by piecewise polynomials with continuous first derivatives. Each material is described by giving its B-H curve and up to three auxiliary (e.g., loss) curves. All material descriptions are identified by user-selected names and titles. Based on fast interactive computer graphics, the editing subsystem permits data entry either numerically or graphically. Various choices of axes, paper distortion, and enlarged plots are permitted. Provision is made for editing, cataloguing, deletion, display, and retrieval of material descriptions. The file management subsystem permits merging or separating the contents of material libraries, as well as exchanging data with external files. View full abstract»

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  • ESCA determination of fluorocarbon lubricant film thickness on magnetic disk media

    Publication Year: 1982 , Page(s): 1073 - 1076
    Cited by:  Papers (15)
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    Fluorocarbon films are in extensive use as lubricants for Winchester-type disks, to reduce disk head wear and to reduce friction during landing and start-up. This paper describes a particularly precise and simple method of measuring the average, relative thickness of such films using ESCA spectroscopy. Film thicknesses are measured with a typical precision of 5% of value (lσ), over the operational range of these films. View full abstract»

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  • Magnetic properties of thin films prepared by continuous vapor deposition

    Publication Year: 1982 , Page(s): 1077 - 1079
    Cited by:  Papers (9)
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    Magnetic thin films deposited by the oblique incidence evaporation are considered to have excellent characteristics for high density recording medium. The magnetic properties and microstructures of these films prepared continuously with a roll coater have been investigated. In continuous vapor deposition, two different modes of deposition processes are considered, corresponding to substrate running direction. The HIN (high incidence nucleation) direction implies that deposition initiates at higher incidence angle and shifts to lower incidence angle. The LIN (low incidence nucleation) direction is the opposite. Hc and Ir/Is of the films by HIN direction have larger values than those by LIN direction in the same region of incidence angle. According to TEM micrographs of thin films by HIN direction, it is observed that elongated nucleation is taken place in higher incidence angle direction and subsequently grown in same direction. View full abstract»

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  • "GT target", A new high rate sputtering target of magnetic materials

    Publication Year: 1982 , Page(s): 1080 - 1082
    Cited by:  Papers (15)  |  Patents (1)
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    A new type of a magnetic material target for high rate sputtering, "Gap Type target (GT target)" have been developed. GT target have many narrow gaps crossing the magnetic flux produced by permanent magnets attached to the cathode. Therefore, the magnetic flux being necessary for magnetron sputtering leaks out over the target surface without magnetic saturation of target materials. By using the GT target, the high rate sputtering of magnetic materials is possible even with common permanent magnets. For example, with a Fe target of 20 mm thick, the deposition rate of 1.5 μm/min. with 15 W/cm2power density is obtained by DC magnetron sputtering at argon pressure of 10^{-2} \sim 1.0 pa. View full abstract»

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  • High coercivity particulate magnetic media via in situ partial reduction of γ-Fe2O3and modified γ-Fe2O3

    Publication Year: 1982 , Page(s): 1083 - 1085
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    First Page of the Article
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  • The DORF effect: Magnetization ripple in particulate media

    Publication Year: 1982 , Page(s): 1086 - 1088
    Cited by:  Papers (2)
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    In 1966, Pearce [1] introduced without analysis the DORF Effect (DisOrientation by Reverse Field) in liquid dispersions of acicular magnetic particles. Bate and Dunn [2] modified orientation magnets to circumvent the effect and produce recording tapes with improved orientation. This paper describes studies of the DORF Effect and analyzes the behavior of particle groups in liquid media when a reverse field is applied. Magnetization reversal occurs by particle group rotation through a symmetric fanning mechanism which shares features with the magnetization ripple phenomenon [3,4] in continuous metal films. The critical field for particle disorientation follows a dipole-dipole interaction relation like that discussed by Jacobs and Bean [5]. For gamma ferric oxide, critical fields are distributed over the range from 20 to 100 Oe. Rotating sample magnetometer data show the DORF Effect is a destruction of uniaxial anisotropy without creation of biaxial or other anisotropies. Hysteresis work in liquid samples is almost totally due to friction between moving particles. View full abstract»

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  • Reverse field orientation effects on rigid disk coating

    Publication Year: 1982 , Page(s): 1089 - 1091
    Cited by:  Papers (2)
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    A reverse magnetic field usually exists for orienting electromagnets used to align particles in magnetic media. Disk disorientation caused by this reverse field, known as the "dorf effect", was found to be a strong function of coating rheology, actual process steps, and reverse field magnitude. Experiments were done on 8-inch and 14-inch rigid disks with coatings of different viscosity varying the most sensitive orientation process parameter, spin-off time. In addition, more controlled experiments were done using 1/2-inch-diameter hand-coated aluminum disks exposed in the gap of an electromagnet to an orienting field followed by varying magnitudes of disorienting fields. Finally, a modified orientation electromagnet with a reduced reverse field was constructed. Our conclusions are that reverse field magnitudes, required to produce significant disorientation are strong functions of coating viscosity, coating formulation, and spin-off times. A 100 Oe reverse field creates a disorienting problem only when using very short spin-off times for coatings of low viscosity, containing a significant portion of high boiling point solvents. Reverse fields larger than 200 Oe, resulting from either high orienting current or a particular electromagnet design, will cause serious disorientation for most magnetic coatings. View full abstract»

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  • Analysis of dropouts in video tapes

    Publication Year: 1982 , Page(s): 1092 - 1094
    Cited by:  Papers (1)  |  Patents (2)
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    A method of correlating digital oscilloscope signals with tape defects to determine causes of dropouts in video tape is described, in the analyses of commercial and experimental home video tapes made from different manufacturers, at least four distinct types of oscilloscope signals were identified. Major sources of dropouts are coating bumps from underlying basefilm asperities and repetitive calendering impressions. View full abstract»

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  • Particle interactions and Hc: An experimental approach

    Publication Year: 1982 , Page(s): 1095 - 1097
    Cited by:  Papers (3)
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    In the phenomenologic relation for the coercivity (Hc) of a powder Hc = A + B(1-P) one generally takes for the volume packing factor P, the "macroscopic" value, which is calculated from the macroscopic dimensions of the sample and the weight. A series of powder with varying pigment volume packing factors were made by densifying the original powder. Applying for these series the Hc vs P relation we have found that for P, the "microscopic" value must be taken. This means that the Hc is primarily controlled by the volume packing factor of the "microscopic" clusters or aggregates. We also found that this "microscopic" P, can easily be measured by means of mercury intrusion porosimetry. View full abstract»

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  • Magnetic characteristics of γ-Fe2O3dispersions

    Publication Year: 1982 , Page(s): 1098 - 1100
    Cited by:  Papers (5)
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    A technique to evaluate the magnetic properties of disc and tape oxide dispersions utilizing a vibrating sample magnetometer has been developed. The method permits an assessment of dispersion quality prior to disc or tape coating and can be utilized to optimize oxide formulations as well as for quality control. View full abstract»

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  • An investigation of magnetic oxides' defects and conflict of anisotropies for diluted powders

    Publication Year: 1982 , Page(s): 1101 - 1103
    Cited by:  Papers (7)
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    Magnetostatic measurements and rotational hysteresis were carried out on extremely diluted samples of pure, surface modified, bulk doped iron oxides and CrO2. It is found that in all these materials but pure γ-Fe2O3a conflict of anisotropy is active. As a result, the values of remanence ratio jrcan be either lower or higher than the theoretical value of ½ for strictly uniaxial particles depending on the angle between the two anisotropy axis and the relative value of the anisotropy constants. It is therefore found that while j_{r} < 1/2 for acicular magnetite and CrO2, the introduction of cobalt always produces an increase of jr: the extreme effect of such conflict can be found in high remanence isotropic particles. Such a conflict is minimized in Surface Modified Materials. From rotational hysteresis, Hcvs. angle with applied field and, over all, from CF and IFF parameters, it is suggested that the postreatment of the iron oxides with the Co-containing solutions, beside the increase of Hc, has a beneficial effect on the morphology of the particles. View full abstract»

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  • Magnetization reversal in sputtered Co-Cr films

    Publication Year: 1982 , Page(s): 1104 - 1106
    Cited by:  Papers (8)
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    The magnetic characteristics of a set of r.f. sputtered Co-Cr films of various composition and thickness are examined in order to evaluate their performance for perpendicular recording. The mechanism of the magnetization reversal is discussed on the bases of: i) the shape of the rotational hysteresis loss as a function of the internal rotating field, ii) the value of the rotational hysteresis integral, iii) the dependence of the coercivity Hc, and the remanence coercivity Hr, on the angle between the easy direction and the field direction. In particular the measurements of rotational hysteresis were performed by monitoring the rate of change of the angular velocity of a top containing the specimen spinning in a magnetic field perpendicular to its axis. The deviation of the experimental behaviour from the ideal models are related to the amount of anomalies in the columnar structure of the film. View full abstract»

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  • Characteristics of RF-sputtered CoCr films

    Publication Year: 1982 , Page(s): 1107 - 1109
    Cited by:  Papers (32)
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    The magnetization of the CoCr recording medium has been investigated by several methods. First the perpendicular hysteresis loops are analysed in the thickness range from 500 to 20,000 Å. This provided evidence that the magnetization process is typefied by domain wall motion. Second the dependence of the coercivity on the film thickness has been determined. The dependence found can be explained if it is assumed, that the coercivity is caused by domain walls, impeded by the crystallite boundaries. Finally stand-still recording experiments have been performed, which confirm that magnetization takes place by the displacement of domain walls. The switching criterion in the writing process is best met by taking the field averaged over the film thickness. View full abstract»

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  • Perpendicular magnetization structure of Co-Cr films

    Publication Year: 1982 , Page(s): 1110 - 1112
    Cited by:  Papers (34)
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    In a perpendicular recording system, a Co-Cr film as a medium is capable of storing very high density signals. Lorentz microscopy of 1000 kV TEM was used to observe the structure of recorded magnetizations in Co-Cr films having perpendicular anisotropy. A composite medium of a Co-Cr film with a soft magnetic back layer was shown by Lorentz microscopy to have a horseshoe magnetization structure. The stable antiparallel magnetization of transition in the Co-Cr layer determined the head-on magnetization structure of the soft magnetic back layer, which consists of a new straw-rope domain structure. The perpendicular magnetization structure of the Co-Cr film was found to consist of small domains magnetized through the film thickness which correspond to the columnar microstructure of the film. Since the intrinsic hysteresis loop of a Co-Cr film was shown to essentially have an ideal rectangular shape, it can be concluded that the Co-Cr layer of a composite film can be recorded by an ideal magnetizing process with negligible demagnetizing field at the transition. View full abstract»

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  • Plasma effects on the Co-Cr deposition in opposing targets sputtering method

    Publication Year: 1982 , Page(s): 1113 - 1115
    Cited by:  Papers (15)
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    It is well known that Co-Cr films show a high perpendicular magnetic anisotropy, coercivity of 1000 oe or above and other properties suitable for perpendicular magnetic recording media. In this report, Co-Cr films, deposited by the bombardment of ions extracted from plasma using a new type of cathode sputtering apparatus with opposing targets, which will be called opposing targets sputtering hereafter, were investigated on morphology, crystal structure and magnetic properties. It was found that in the Co-Cr films of suitable magnetic properties for recording media, the morphology changes and the degree of C-axis orientation of Co-Cr hcp crystal, Δθ50is a constant value as low as about 3° with the increase of ion bombardment energy during deposition. Both morphology and the dependency of Δθ50on thickness of the Co-Cr films deposited by the opposing targets sputtering considerably differ from those by RF sputtering. There was no columnar structure observed in the cross section of the Co-Cr films suitable for perpendicular magnetic recording media prepared by the opposing targets sputtering, whereas columnar structure is reported to be observed clearly in the case of both RF sputtering and vacuum vapor deposition. View full abstract»

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  • Co-V films for perpendicular recording

    Publication Year: 1982 , Page(s): 1116 - 1118
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    Co-V films with the c-axis of the hcp structure strongly oriented normal to the film plane were prepared by RF-sputtering. The formation of a perpendicular magnetic recording mode was inferred from the measurement of the recording characteristics. It was also found that the anisotropy field (Hk) of the recording medium did not always need to exceed the demagnetizing field (4πMs) in order to display perpendicular recording. 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