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Magnetics, IEEE Transactions on

Issue 1  Part 1 • Date Jan. 2007

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Displaying Results 1 - 18 of 18
  • [Front cover]

    Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Page(s): C2
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  • Table of contents

    Page(s): 1
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  • Nonequilibrium Magnetic Domain Structures as a Function of Speed of Switching Process in Ni 80Fe20 Thin-Film Element

    Page(s): 2 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    The influence of the speed of the switching process on the nonequilibrium domain structures in magnetic thin-film elements undergoing large angle rotations was studied with time-resolved scanning Kerr microscopy and numerical modelings. In particular, the systematic evolution of the spatiotemporal nature of the reversal of a small Ni80Fe20 element to progressively faster switching fields has been investigated. Generally, the magnetization evolves into a complex domain structure in nonequilibrium state when a magnetic element is excited by applying a short magnetic field pulse. The degree of complexity of the nonequilibrium domain structure is found to be a strong function of the speed of the switching process View full abstract»

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  • Ni-Zn Ferrites Composites With Almost Equal Values of Permeability and Permittivity for Low-Frequency Antenna Design

    Page(s): 6 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Composites based on ferrite powders Ni0.95-xZnxCo0.05Fe1.90Mn0.02 O4 with x=0-0.25, with a volume concentration of 50%, were fabricated and characterized. Dielectric and magnetic properties of the composites were measured over 0.01-16.5 GHz. The permeability of the composites at low frequency increases from ~4.18 to ~7.85 as the contribution of Zn is increased from x=0 to x=0.25, while the permittivity remains almost unchanged with x. The composites based on the ferrite powders with Zn of x=0.10-0.25 have almost equal values of epsiv' and mu' at low frequency (<30 MHz). With the low magnetic and dielectric loss tangent, these materials are useful to the design of miniaturized antennas over 2-30 MHz View full abstract»

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  • Linear Step Motor Based on Magnetic Force Control Using Composite of Magnetostrictive and Piezoelectric Materials

    Page(s): 11 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (991 KB) |  | HTML iconHTML  

    We assemble a composite of giant magnetostrictive material (Terfenol-D) and stack piezoelectric transducer (PZT) actuator, and use it in a linear step motor. Control of the magnetic force exploits the inverse magnetostrictive effect of the Terfenol, in which the composite and a magnetic circuit in combination controls the magnetic force on a movable yoke with the voltage of the PZTs via mechanical stress. The unique feature of this arrangement is zero power consumption needed to maintain a constant magnetic force; once the PZTs have been charged, no current flows in static operation due to the capacitive property. A composite having simple configuration, bonding both Terfenol and PZT to iron yokes, is verified to control the magnetic force over wide variations under appropriate prestress conditions. A linear step motor with four composites as a stator also demonstrates variation of the thrust force and the possibility of motion control. Microstep motion of the mover was achieved using sinusoidal voltage, and zero current was observed with stationary voltage. The principle should be advantageous in high-precision positioning View full abstract»

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  • Modeling of Magnetically Levitated Planar Actuators With Moving Magnets

    Page(s): 15 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2137 KB) |  | HTML iconHTML  

    This paper presents three types of magnetostatic models of ironless planar actuators with moving magnets. The models predict the force and torque exerted on the translator of the actuator, which can be positioned in six degrees-of-freedom with respect to the stator coils. The force and torque are calculated with the Lorentz force law. The analytical and numerical models can be used for the design of large planar actuators, for the fast comparison of actuator topologies, and in the decoupling and commutation algorithm. The models have been verified with experiments View full abstract»

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  • Modeling and Analysis of Eddy-Current Damping for High-Precision Magnetic Levitation of a Small Magnet

    Page(s): 26 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (873 KB) |  | HTML iconHTML  

    This paper presents modeling and analysis of eddy-current damping that is formed by a conductive plate placed below the levitating object in order to suppress vibrations and ensure stability. It is demonstrated that vibrations should be damped to preserve stability and precision especially for stepwise motion. The levitated object is a small permanent magnet in our experiments. A magnetic drive unit is used for vertical motion of the magnet. Eddy-current distribution in the plate is calculated by solving diffusion equation for vector magnetic potential. The eddy force applied to the object is derived by a coil model representation. It is shown that if a 20 mm radius, 9 mm thick aluminum circular plate is used for eddy-current damping, the levitated object can closely follow a step input with a steady-state precision varying between 0.04 and 0.07 mm depending on the plate object distance. Eddy-current damping is a key technique that improves levitation performance to increase the diversity of applications of magnetic levitation systems in micromanipulation and microelectronic fabrication View full abstract»

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  • Enhanced Modeling of Linear Permanent-Magnet Synchronous Motors

    Page(s): 33 - 39
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB) |  | HTML iconHTML  

    Modeling of air-gap flux density distribution produced by magnet poles is essential for analysis and design of linear permanent-magnet synchronous motors. This is usually done by time-consuming numerical methods which are difficult to be incorporated in iterative motor design procedures or by approximate models which lack desirable accuracy. This paper presents an alternative method to model the air-gap flux density distribution which is both accurate and simple enough to be integrated into iterative motor design procedures. It consists of the solution of an improved magnetic equivalent circuit and an air-gap flux density distribution function (FDDF). The end teeth effects and magnetic saturation of iron core can be taken into account in the modeling. Different motor characteristics are calculated by means of the proposed FDDF. The accuracy of the proposed method in modeling of the machines is verified by the finite-element method and its superiority over a recent method based on an extensive machine model is demonstrated View full abstract»

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  • Reduction of the Cogging Force at the Outlet Edge of a Stationary Discontinuous Primary Linear Synchronous Motor

    Page(s): 40 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1454 KB) |  | HTML iconHTML  

    Recently, permanent-magnet-type linear synchronous motors (PM-LSMs) have been used as a driving source of transportation systems, to satisfy requirements such as speeding up of transportation systems and also to simplify maintenance. The authors' laboratory has proposed a stationary discontinuous primary PM-LSM in which the primary is engaged only when accelerated and decelerated operation is necessary, in order to resolve the problem of higher costs, when PM-LSM is used with long-distance transportation systems in factories. However, the stationary discontinuous primary PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the primary. These edges become a problem, because the cogging force that they exert influences the controllability of the motor. This paper presents the results of an experimental examination and three-dimensional (3-D) numerical analysis by the finite-element method (FEM) of the cogging force exerted by the outlet edge. Moreover, we deformed the shape of the primary to decrease the cogging force at the outlet edge, and the results are examined using 3-D numerical analysis by the FEM View full abstract»

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  • Drive of Single-Phase Brushless DC Motors Based on Torque Analysis

    Page(s): 46 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    The high torque peaks commonly found in single-phase brushless dc motors can be compressed by different driving methods, which are proposed and studied based on finite-element analysis (FEA). It is concluded that one dead-zone can be added into the driving signals to improve current waveforms and torque envelope. The test results show that the noise level and performances are greatly improved when one proper dead zone is implemented View full abstract»

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  • Optimal Design and Control of a Wheel Motor for Electric Passenger Cars

    Page(s): 51 - 61
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB) |  | HTML iconHTML  

    An optimal design and control technology of a wheel motor is proposed for small electric passenger cars. The axial-flux sandwich-type disc motor is designed with a rotor embedded with neodymium-iron-boron (NdFeB) magnets and two plates of stators, and is directly mounted inside the wheel without mechanical transmission and differential gears. Sensitivity analyses are performed to choose critical design parameters, which are the most influential in design objectives, to maximize the driving torque, efficiency, rated speed, and to minimize the weight of motor under various constraints of size, materials, and power sources. The optimal driving current waveform is proven to be the same as the fundamental harmonic of the back electromotive force to produce maximum torque with least ripples. The finite-element refinement results in the motor prototype with a maximum torque over 38 kgmiddotm and a corresponding torque density of about 1.72 kgmiddotm/kg at the maximum allowable phase current of 50.25 A (rms). Two such rear driving wheels are able to drive a 600 kg passenger car to accelerate from 0 to 40 km/h in 5 s on a 15 degree incline. This dedicated wheel motor is applicable to pure or hybrid electric vehicles as a promising solution to the direct-driven electric vehicle View full abstract»

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  • Thermal Management in Heat-Assisted Magnetic Recording

    Page(s): 62 - 66
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    A slider thermal characterization system is described. A model for the dissipation of heat applied to the air-bearing surface of a hard disk drive slider is introduced. The model's predictions are compared to the measured results from the characterization system. A modification to the model is shown to compensate for the experimental difference and indicates that thermal loads on a slider can be managed by a combination of physical separation and increased thermal conductivity in the regions where thermal loads occur View full abstract»

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  • Minimum-Latency Tracking of Rapid Variations in Two-Dimensional Storage Systems

    Page(s): 67 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (931 KB) |  | HTML iconHTML  

    The trend of increasing storage densities results in growing sensitivity of system performance to variations of storage channel parameters. To counteract these variations, more adaptivity is needed in the data receiver. Accurate tracking of rapid variations is limited by latencies in the adaptation loops. These latencies are largely governed by delays of the bit detector. In two-dimensional storage systems, data are packaged in a group of adjacent tracks or rows, and for some of the rows the detection delays can increase dramatically with respect to one-dimensional systems. As a result, the effective latencies in the adaptation loops preclude the tracking of rapid variations and really limit the performance of the system. In this paper, a scheme is proposed that overcomes this problem and that can be used for timing recovery, automatic gain control, and other adaptive circuits. Rapid variations for all the rows are tracked using control information from rows for which detector latency is smallest. This works properly if rapid variations are common across the rows as is the case, for example, for the two-dimensional optical storage (TwoDOS) system. Experimental results for TwoDOS confirm that the scheme yields improved performance with respect to conventional adaptation schemes View full abstract»

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    Page(s): 79
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  • IEEE Magnetics Society & The IEEE Press call for books

    Page(s): 80
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  • IEEE Magnetics Society Information

    Page(s): C3
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  • IEEE Transactions on Magnetics institutional listings

    Page(s): C4
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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