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Magnetics, IEEE Transactions on

Issue 2 • Date March 2002

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Displaying Results 1 - 19 of 19
  • Correction to "Comparison of the normal and initial induction curves"

    Publication Year: 2002 , Page(s): 1447
    Cited by:  Papers (1)
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  • Inclusive model of ferromagnetic hysteresis

    Publication Year: 2002 , Page(s): 1326 - 1332
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (503 KB) |  | HTML iconHTML  

    We present an inclusive macroscopic model of ferromagnetic hysteresis. We developed the model from a Stoner-Wohlfarth approach by adding the mean-field or nearest-neighbor interactions and the effect of pinning. The model includes features of the Jiles-Atherton model in the previous Atherton-Beattie extension of the Stoner-Wohlfarth model, but still omits the domain wall energy effects included in the Globus model. The model describes both reversible and irreversible processes and hysteresis caused by combinations of interaction, anisotropy, and pinning. We outline computational approaches and give examples View full abstract»

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  • Modeling eddy currents with boundary conditions by using Coulomb's law and the method of images

    Publication Year: 2002 , Page(s): 1333 - 1340
    Cited by:  Papers (10)
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    Since the eddy-current problem usually depends on the geometry of the moving conductive sheet and the pole shape, there is no general method for solving it analytically. This paper presents a method for analysis of the eddy current in the special case of a rotating disk in a time-invariant field. The analysis uses Coulomb's law and the method of images to consider the boundary conditions. First, the surface charge generated in the rotating disk is obtained and Coulomb's law is applied to calculate the electric field intensity, assuming an infinite disk radius. Second, the finite disk radius is taken into account by introducing an imaginary electric field intensity to satisfy the boundary condition that the radial component of the eddy current is zero at the edge of the rotating disk. Third, the braking torque is calculated by applying the Lorentz force law. The paper compares the computed braking torque with the experimental results to establish the validity of the model View full abstract»

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  • Two-dimensional Cartesian air-gap element (CAGE) for dynamic finite-element modeling of electrical machines with a flat air gap

    Publication Year: 2002 , Page(s): 1357 - 1360
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    This paper extends the air-gap element (AGE) to enable the modeling of flat air gaps. AGE is a macroelement originally proposed by Abdel-Razek et al. (IEEE Trans. Magn., vol. 17, pp. 3250-3252, 1981; ibid., vol. 18, pp. 655-659, 1982) for modeling annular air gaps in electrical machines. The paper presents the theory of the new macroelement and explains its implementation within a time-stepped finite-element (FE) code. It validates the solution produced by the new macroelement by comparing it with that obtained by using an FE mesh with a discretized air gap. It then applies the model to determine the open-circuit electromotive force of an axial-flux permanent-magnet machine and compares the results with measurements View full abstract»

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  • TixZr1-x underlayers for CoCrPtB perpendicular magnetic recording media

    Publication Year: 2002 , Page(s): 1436 - 1440
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    We describe the effects of TixZr1-x underlayers on the microstructural and magnetic properties of CoCrPtB layers. We found that as the Zr atomic composition increases in the Ti xZr1-x underlayers, the unit cells of the Tix Zr1-x underlayers expand. The TixZr1-x (0002) texture is strongest as the Zr atomic composition ranges from 40% to 60%. In addition, the CoCrPtB (0002) texture induced by the (0002) textured TixZr1-x underlayer is enhanced at these optimizing Zr compositions. The grain size of the CoCrPtB layers deposited onto the TixZr1-x, underlayers is around 7.5-9.5 nm. Stacking fault streaks observed by transmission electron microscopy indicate that stacking faults exist in the CoCrPtB films with the TixZr1-x underlayers. The Hc (coercivity) and S* (squareness) of the CoCrPtB magnetic layers deposited onto the pure Ti and Zr underlayer were higher than those with the TiZr alloy underlayers View full abstract»

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  • Electrical modeling of transformer connecting bars

    Publication Year: 2002 , Page(s): 1378 - 1382
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB) |  | HTML iconHTML  

    Traditionally, connections in high-voltage, high-current, and low-frequency circuits are always considered as perfect short circuits, so to analyze their contribution to electrical performance of a structure is not considered necessary. We show here that, even for low-frequency structures, the electrical parasitic characteristics of cabling can lead to some unexpected performances. In particular, our study of outside connections of a 400 MVA transformer has shown current imbalances between the three phases and inside the phases. We achieved this by using a semianalytical method that is presented in this paper. Results show the need to model this part of the structure. This method has advantages over numerical techniques of calculation View full abstract»

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  • Microwave properties of ZnTi-substituted M-type barium hexaferrites

    Publication Year: 2002 , Page(s): 1391 - 1394
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (245 KB) |  | HTML iconHTML  

    We have prepared magnetic anisotropic polycrystalline hexaferrites Ba(ZnTi)xFe12-2xO19 with high orientation degrees f and low dielectric loss tangent tgδε by standard ceramic techniques with magnetic alignment of the grains' c axis during wet pressing and in flowing-oxygen sintering. When x increases, the saturation magnetization Ms, the Curie temperature Tc, and the anisotropy field Ha of the hexaferrites decrease. The results can be interpreted by assuming that Zn2+ ions replace Fe3+ ions of the tetrahedral 4f1 sites and hexahedral 2d sites while Ti4+ ions replace spin up Fe3+ ions of octahedral sublattices 12k and 2a View full abstract»

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  • Thermal micromagnetic model with a pseudo-three-dimensional junction for magnetoresistive heads

    Publication Year: 2002 , Page(s): 1395 - 1404
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    We developed a pseudo-three-dimensional (3D) thermal model in conjunction with a thermal micromagnetic model to study the performance of magnetoresistive (MR) readers. With decreasing sensor dimensions, the junction plays an important role in the overall sensor response. With an image method, we converted the 3D thermal problem to a set of coupled nonlinear differential-integral equations in three regions: sensor stack region, junction region, and lead region. Analytic methods for each region allow a speedy solution for rapid development in MR head design and performance analysis, such as numerical design of experiments and regression for design optimization, Monte Carlo analysis, and statistical analysis for product yield View full abstract»

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  • Influence of stator slot geometry and rotor eccentricity on field distribution in cylindrical magnetic actuators

    Publication Year: 2002 , Page(s): 1348 - 1356
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (457 KB) |  | HTML iconHTML  

    The paper presents an analytical method for computing the instantaneous air-gap flux distribution in cylindrical magnetic actuators with slotted stators and rotor eccentricity. The method does not rely on permeance functions; therefore, the resulting flux distribution can be used to compute actuator properties such as negative stiffness, cogging torque, and back-emf. The method uses Fourier series expansions to model current distributions and permanent magnets as sources of magnetomotive force (MMF) on the air-gap boundary and then solves the Dirichlet boundary value problem in the eccentric annulus for the MMF within the permanent magnet and air gap regions. It accounts for the slotting effect by adding a boundary perturbation step to the solution that includes the decreased permeance of the slots. The method is applied to a sample problem that examines both the effects of slot length and slot width on negative stiffness coefficients. The method is benchmarked against finite-element solutions; the two models agree well up to a certain critical slot length. This critical slot length corresponds to the traditional infinite slot length (that slot length beyond which no appreciable change in flux distribution occurs). While the method is applied to a permanent magnet motor of internal rotor construction, it is generally applicable to many actuator topologies View full abstract»

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  • Obtaining the operating characteristics of linear induction motors: a new approach

    Publication Year: 2002 , Page(s): 1365 - 1370
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (245 KB) |  | HTML iconHTML  

    We modified, by means of the finite-element method (FEM), the model suggested by Duncan (Proc. IEE, pt. B, vol. 130, no. 1, 1983) for simulation of linear induction motors. The modified model covers the special phenomena in linear motors such as transverse edge effect, longitudinal end effect, and saturation of back iron. The modified model first computes the level of saturation by simple equations and an iterative method. Then, using the FEM, it computes the equivalent circuit parameters. Finally, it uses the Duncan model to account for the end effect. The modified model thus can be used to design linear induction motors. Furthermore, the change in equivalent circuit parameters at different operating conditions can be taken into account. A comparison of the simulation results based on the proposed model with experimental measurements shows the high accuracy of the model View full abstract»

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  • Simulation of the off-track capability of a one terabit per square inch recording system

    Publication Year: 2002 , Page(s): 1429 - 1435
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (395 KB) |  | HTML iconHTML  

    We investigated the potential of extending conventional magnetic recording technology to a one terabit per square inch (Tb/in2) density using a simple model, focusing on the off-track capability of a hypothetical perpendicular recording system. Our simulation considered the medium's granular structure, head side reading, and side writing. However, as a first approximation, interactions between grains were neglected. We investigated the characteristics of both an isolated transition and a pseudorandom sequence. The signal-to-noise ratio is very low (around 10 dB) at such a density. Direct bit-by-bit simulation on 80000 bits of a 1023-bit pseudorandom sequence yielded the bit-error rate (BER). By changing the squeeze position of the side track, a series of "bathtub" curves was calculated and thus, 747 curves at various BER thresholds were investigated. We also studied different detection schemes and the block failure rate after error-correction code View full abstract»

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  • Micromagnetic analysis of the effect of intergranular exchange on thermal stability in magnetic recording. II. Slightly oriented longitudinal media

    Publication Year: 2002 , Page(s): 1417 - 1421
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    For pt.I see ibid., vol.38, no.2, p.1405-16 (Mar. 2002). We describe micromagnetic simulations to examine the effect of intergranular exchange on thermal stability of dibit transitions in slightly oriented longitudinal media. We found that, by increasing the intergranular exchange and the anisotropy orientation ratio, Ku⟨V⟩ is reduced to maintain the fixed Mrt, the writing coercivity, and the average grain planar area. Within the drive working temperatures (T⩽350 K), to increase signal-to-noise ratio (SNR) at 109 s, both the intergranular exchange and the anisotropy orientation ratio must be reduced. However, if both Ku ⟨V⟩ and Mrt are fixed, for a constant circumferential loop closure field, a larger SNR is always exhibited at a higher OR(Mr) initially and at 109 s. For both cases, if the intergranular exchange cannot be neglected, SNR always slightly increases with increasing OR(Mr) View full abstract»

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  • Prediction of track misregistration due to disk flutter in hard disk drive

    Publication Year: 2002 , Page(s): 1441 - 1446
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    Disk runout consists of repeatable runout (RRO) and nonrepeatable runout (NRRO). NRRO is the main cause of track misregistration that prevents a high track density, whereas tracking servo control can compensate for most of RRO. An increase in the disk rotation speed increases the amplitude of disk flutter and, hence, causes head position error. Disk flutter is mainly caused by air disturbance due to disk rotation. In this paper, the displacement spectrum is obtained by integrating the velocity data and removing the low-frequency component associated with integration noise. The axial displacements are converted to radial track misregistration units by modal analysis, the reformed Barasch method, and experimental study of the disk. The interaction between head and disk is precisely solved, and it becomes possible to predict the track misregistration by analyzing the disk flutter and transfer ratio for various disks View full abstract»

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  • Analytical method for eddy current loss in laminated rotors with magnetic bearings

    Publication Year: 2002 , Page(s): 1341 - 1347
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB) |  | HTML iconHTML  

    This paper presents a totally analytical method to calculate the eddy current loss in a laminated rotor. First, the method derives the analytical field solutions both in the lamination and the air gap with average boundary conditions at the surface of the rotor. The magnetic field can then be determined from the static flux distribution around the pole surface. Then, the method obtains the eddy current induced in the lamination from the field solution in the lamination. Finally, it calculates the rotation loss by integrating resistive power loss over the volume of the lamination and summed in all sheets. The results show good agreement with experimentally measured losses View full abstract»

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  • Review of dynamic stability of repulsive-force maglev suspension systems

    Publication Year: 2002 , Page(s): 1383 - 1390
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (214 KB) |  | HTML iconHTML  

    This review summarizes and assimilates the results of work reported in the literature over the past 25 years that pertains to understanding those factors that influence the dynamic stability of repulsive-force magnetic levitation (maglev) suspension systems. The review includes summaries of the results of representative tests of large-scale vehicles on linear test tracks and of analytical and laboratory-scale investigations of stability and dynamics of electrodynamic suspension systems. Research needs are also addressed View full abstract»

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  • Study of triangular winding alternators

    Publication Year: 2002 , Page(s): 1361 - 1364
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (299 KB) |  | HTML iconHTML  

    This study examines a three-dimensional magnetic flux machine as a replacement for the alternator of a car. Such a machine could be placed in the clutch bell housing. The windings have a triangular shape so that the end windings take up less space. This single-phase machine is very thin. Both triangular and rectangular magnet shapes have been studied for the rotor. Here, we present two models for studying the behavior of such machines: an analytical no-leakage model and a more complete finite-element model. We use both models to describe a homopolar machine and a heteropolar machine and compare them to conventional machines with rectangular windings and rectangular magnets View full abstract»

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  • Minimizing torque ripple in permanent magnet synchronous motors with polymer-bonded magnets

    Publication Year: 2002 , Page(s): 1371 - 1377
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB) |  | HTML iconHTML  

    The paper presents a method for determining the main design parameters of a permanent magnet (PM) motor that will reduce the total torque ripple. First, the magnet arrangement is derived by one-dimensional field analysis coupled with a multiobjective minimization technique. Then, a two-dimensional model is used to further optimize the magnet arc width and minimize the cogging torque. The analysis mainly focuses on a rotor that is completely covered by the permanent magnets. In this configuration, the permanent magnets can be made from a tube of polymer-bonded magnet, and manufacture of the motor is greatly simplified. We present experimental tests of a machine manufactured on the basis of our design procedure View full abstract»

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  • Micromagnetic analysis of the effect of intergranular exchange on thermal stability in magnetic recording. I. Two-dimensional isotropic longitudinal media

    Publication Year: 2002 , Page(s): 1405 - 1416
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    We describe micromagnetic simulations that examine the effect of intergranular exchange on thermal stability of dibit transitions in two-dimensional (2D) isotropic longitudinal media. We found that, by maintaining the constant Mrt, the writing coercivity and the average grain planar area, Ku ⟨V⟩ is reduced with increasing he. Increasing the intergranular exchange enhances thermal decay and yields a smaller signal-to-noise ratio (SNR) at 109 s. However, if both Ku⟨V⟩ and Mrt are fixed, ⟨D⟩ increases slightly if the writing coercivity is held constant but decreases slightly at a fixed intrinsic loop closure field. For both cases, a smaller SNR is always found at a higher exchange initially and after ten years. Thus, for 2D isotropic longitudinal media, the intergranular exchange must be reduced to achieve a higher SNR at 109 s View full abstract»

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  • Micromagnetic analysis of the effect of intergranular exchange on thermal stability in magnetic recording. III. Perpendicular media

    Publication Year: 2002 , Page(s): 1422 - 1428
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    We describe micromagnetic simulations to examine the effect of intergranular exchange on thermal stability of dibit transitions in perpendicular media. We found that, without an intergranular exchange, pure magnetostatic interactions induce substantial magnetization decay; a weak exchange, however, reduces the decay significantly. In addition, the reduction is more pronounced at reduced magnetostatic interactions. To achieve a high signal-to-noise ratio (SNR) and reduce thermal decay simultaneously, a medium with reduced magnetostatic interactions is required and a weak exchange should be included. Reducing the spacing between the soft underlayer and the recording medium enhances thermal stability. The effect is more pronounced at higher linear densities 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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Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology