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Magnetics, IEEE Transactions on

Issue 10 • Date Oct. 2007

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Displaying Results 1 - 25 of 27
  • [Front cover]

    Publication Year: 2007 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2007 , Page(s): C2
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  • Table of contents

    Publication Year: 2007 , Page(s): 3805 - 3806
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  • Using a Single Toroidal Sample to Determine the Intrinsic Complex Permeability and Permittivity of Mn–Zn Ferrites

    Publication Year: 2007 , Page(s): 3807 - 3815
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (954 KB) |  | HTML iconHTML  

    Analysis of the principle of the published lumped circuit methods for determination of the intrinsic complex permeability and permittivity of the Mn-Zn ferrites reveals that as long as the electric and the magnetic field distributions in the core(s) in two measurements are different, the two intrinsic values can be determined. Using this principle, we developed a set of general lumped circuit methods based on a toroidal Mn-Zn ferrite core as the measurement sample. We examined two possible different excitation modes: magnetic field excitation and electric field excitation. The two different excitation modes result in significantly different field distributions in the sample. Thus, high accuracy can be guaranteed in principle. For the magnetic field excitation, we present in this paper a general finite-difference method to solve the fields in the core and the impedance of the ferrite core inductor. To avoid the stray capacitance among the coils of the ferrite core winding inductor in the measurement, we made a set of short-ended coaxial test fixtures. We performed experiments to determine the intrinsic complex permeability and permittivity of a Mn-Zn ferrite core up to 10 MHz by using the two general methods and validated the measured intrinsic values experimentally. View full abstract»

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  • Investigating the Characteristics of Cobalt-Substituted MnZn Ferrites by Equivalent Electrical Elements

    Publication Year: 2007 , Page(s): 3816 - 3820
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (633 KB) |  | HTML iconHTML  

    We investigated the electrical and magnetic properties of cobalt-substituted manganese-zinc soft ferrite by using the equivalent lumped elements acquired from the appropriate equivalent electrical circuit of polycrystalline ferrite. We applied the equivalent lumped circuit, combined with equivalent lumped resistances and capacitance, to determine the effect of microstructure on electrical and magnetic properties of cobalt-substituted manganese-zinc ferrites. Both the hysteresis loss and the eddy-current loss of soft ferrites account for a major proportion of iron loss in high-frequency switching mode power supplies. Replacing a small portion of Fe2+ with Co2+ remarkably increases the bulk resistivity of the MnZn ferrite and decreases the core loss by lowering eddy-current loss. A longer isothermal duration causes grain growth and forms a larger equivalent capacitance, which leads to a reduction in hysteresis loss. However, excess substitution of Co2+ for Fe2+ is disadvantageous to magnetic permeability and raises core loss. We measured the dc resistivity by the four-probe method on sintered disks with both sides polished and coated with a thin layer of silver paste as a good contact material. We measured the magnetic permeability by an impedance analyzer at room temperature. The total loss of Mn0.58Zn0.37 Co0.01Fe2.04O4 ferrite core does not exceed 420 mW/cm3 at 300 kHz/70 mT. View full abstract»

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  • Comparison of Micromagnetic and Point Probe Model in Magnetic Force Microscope Simulation

    Publication Year: 2007 , Page(s): 3821 - 3825
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (366 KB) |  | HTML iconHTML  

    We developed a micromagnetic model of magnetic force microscopy (MFM) tip to compare it with the simple point probe model. We simulated the MFM signal to provide an understanding of the measurement of the field generated by the write head in perpendicular recording hard disk drives. When the magnetic pole density at the air-bearing surface of the head's main pole is increased from 0.2 T to 1 T, the MFM tip with vertical anisotropy shows a flower-state magnetization, while the tip with horizontal anisotropy has more complicated switching modes. It is found that the signal ratio of the two MFM tips with vertical/horizontal anisotropy does have a one-to-one correspondence to the average magnetic field in the tip; however, the signal ratio may change sign because of the magnetic moments' switching in the tip with vertical anisotropy. The result of micromagnetic simulation is quite similar to that of the point probe model, and has good agreement with experiments. View full abstract»

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  • General Expressions for the Magnetic Flux Density Produced by Axially Magnetized Toroidal Permanent Magnets

    Publication Year: 2007 , Page(s): 3826 - 3832
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    This paper presents analytical-integral expressions which evaluate the magnetic flux density radial and axial components' on- and off-axis of axially magnetized toroidal permanent magnets. The pieces, when used in magnetic electron beam focusing structures called periodic-permanent magnets (PPMs), can be employed in microwave vacuum electronics devices. These expressions can be adapted to computational algorithms, especially those developed based on mathematical commercial codes, aiding the investigation of the effect of magnetic fields on electron beam dynamics. Comparisons between analytical-integral expressions and theoretical and experimental data are also presented and discussed. View full abstract»

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  • Computation of the Three-Dimensional Magnetic Field From Solid Permanent-Magnet Bipolar Cylinders By Employing Toroidal Harmonics

    Publication Year: 2007 , Page(s): 3833 - 3839
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (854 KB) |  | HTML iconHTML  

    We present an analytical method, employing toroidal harmonics, for computing the three-dimensional (3-D) magnetic field from a circular cylindrical bipolar permanent magnet. Bipolar magnets are those which are polarized perpendicular to the axis of the cylinder. We take a completely analytical approach in order to facilitate parametric studies of the external 3-D magnetic field produced by bipolar magnets. The results of our analysis are verified by comparing them to previously published results. The application of toroidal harmonics are ultimately shown to be well-suited for both parametric studies as well as numerical computation. View full abstract»

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  • Modeling High-Frequency Multiwinding Magnetic Components Using Finite-Element Analysis

    Publication Year: 2007 , Page(s): 3840 - 3850
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (831 KB) |  | HTML iconHTML  

    This paper presents a magnetic component equivalent circuit as well as a methodology to extract its parameters by using a finite- element analysis tool. The model is valid for any kind of magnetic component-transformers and gapped and nongapped inductors-and takes into account frequency and geometry effects such as skin, proximity, interleaving, gap, and end effects. An additional model for capacitive effects may be coupled with the previous one to obtain a more precise result. The impedances in this model represent not only the self terms, but also all mutual terms shared between the windings. Because the simplification of concentrating impedances in one winding is not invoked, simultaneous conduction of all windings (such as forward-like converters) or in alternate conduction of the windings (such as flyback-like converters) can be accurately simulated. The parameters of these self and mutual impedances are frequency dependent, so the model represents the frequency behavior of windings in detail. This allows simulating components with nonsinusoidal currents like the ones present in switched-mode power supplies, provided there is no saturation of magnetic materials. This is not a serious limitation of the model because this kind of power supply works in linear (no-saturation) mode. When there is saturation, the core model determines the component behavior. Applying the model to several actual components has shown its usefulness and accuracy. Details concerning model parameters extraction are presented here with simulation and measurement results. View full abstract»

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  • Inductor Modeling in Wireless Links for Implantable Electronics

    Publication Year: 2007 , Page(s): 3851 - 3860
    Cited by:  Papers (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (690 KB) |  | HTML iconHTML  

    This paper describes the ac power dissipation of coils as well as their self-capacitance, self-resonant frequency, and quality factor Q. In the past, self-resonant frequency was rarely calculated during design because of the lack of suitable closed-form design equations. However, coils are widely used in biomedical applications as inductive links for both power and data, and the power transfer capacity and the data rate of inductive links are determined by the operating frequency of the coils. The maximum operating frequency is limited by the self-resonant frequency of the coil. We present here an analytical express for the optimal frequency of a coil in terms of the design parameters. By varying the design parameters, we can move the optimal frequency close to the operating frequency, thereby boosting the efficiency of the inductive link. We have verified the derivation experimentally and shown it to be useful in optimizing coil Index performance. View full abstract»

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  • Analytical Interpretation and Quantification of Rotational Losses in Stator Cores of Induction Motors

    Publication Year: 2007 , Page(s): 3861 - 3867
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB) |  | HTML iconHTML  

    We propose an approach to allocate and delimit a region in which the rotational losses are of most importance in the stator core of induction motors. The delimitation is based on the analysis of points at which the minimum flux density is not null. The analysis of flux paths and values of flux density over a number of motors allows a model of flux density to be proposed for the chosen rotational region. We conducted the process by post-processing finite-element results. A comparison with bench test results shows that the approach can confine the effects of rotational losses within a region allocated in the tooth roots without significant loss of accuracy. We give analytical expressions based on geometrical data. The approach provides a quick method to evaluate the rotational losses by analytical means, bypassing the use of numerical methods at those design stages at which is preferable to reduce the accuracy in favor of computational speed. View full abstract»

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  • Compensation Scheme of Position Angle Errors of Permanent-Magnet Linear Motors

    Publication Year: 2007 , Page(s): 3868 - 3871
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (359 KB) |  | HTML iconHTML  

    The position angle is very important in the current control of permanent-magnet linear motors (PMLMs), and its error affects the control precision of currents. However, the position angle is often not accurately detected because of faults in motor making, pulse loss of linear encoders, and so on. In order to precisely control the currents of PMLMs, a compensation scheme of position angle errors is proposed based on the mathematical relation between position angle errors and currents. In the scheme, a position angle error compensator is designed to compensate the position angles detected by linear encoders. Furthermore, a filter and a class of iteration learning algorithm are proposed to avoid the errors produced by detected phase currents and phase voltages. Simulation results show that position angle errors of PMLMs are fully compensated. Using the designed position angle error compensator, currents can be controlled in a more precise manner. View full abstract»

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  • Analytical Solution of Air-Gap Field in Permanent-Magnet Motors Taking Into Account the Effect of Pole Transition Over Slots

    Publication Year: 2007 , Page(s): 3872 - 3883
    Cited by:  Papers (43)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (669 KB) |  | HTML iconHTML  

    We present an analytical method to study magnetic fields in permanent-magnet brushless motors, taking into consideration the effect of stator slotting. Our attention concentrates particularly on the instantaneous field distribution in the slot regions where the magnet pole transition passes over the slot opening. The accuracy in the flux density vector distribution in such regions plays a critical role in the prediction of the magnetic forces, i.e., the cogging torque and unbalanced magnetic pull. However, the currently available analytical solutions for calculating air-gap fields in permanent magnet motors can estimate only the distribution of the flux density component in the radial direction. Magnetic field and forces computed by the new analytical method agree well with those obtained by the finite-element method. The analytical method provides a useful tool for design and optimization of permanent-magnet motors. View full abstract»

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  • Saturation Effects on Unbalanced Magnetic Pull in a Hydroelectric Generator With an Eccentric Rotor

    Publication Year: 2007 , Page(s): 3884 - 3890
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (333 KB) |  | HTML iconHTML  

    We report an investigation of saturation effects on the unbalanced magnetic pull in a hydroelectric generator with 20% static eccentricity. We determine the magnetic pull force by the finite-element method in parallel with a simple analytical model for various no-load voltages and loads. Saturation significantly affects the magnitude of the unbalanced magnetic pull for high voltages and large loads. View full abstract»

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  • Novel Microrobots and Micromotors Using Lorentz Force Driven Linear Microactuators Based on Polymer Magnets

    Publication Year: 2007 , Page(s): 3891 - 3895
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3331 KB) |  | HTML iconHTML  

    This paper reports on the development of several novel microelectromechanical systems (MEMS) machines based on linear Lorentz force actuators. These were monolithically fabricated and include micromachined polymer magnets. Polymer magnets allow a highly flexible definition of magnetic areas, arbitrary shape, and properties. By combining these linear actuators with mechanical compliant structures using Epon SU-8, we were able to build in-plane and out-of-plane micropositioners, micromotors, and microgrippers. View full abstract»

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  • A Sensorless Method for Controlling the Closure of a Contactor

    Publication Year: 2007 , Page(s): 3896 - 3903
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    We propose a new closed-loop sensorless method for reducing contact bounce on closure of a contactor. Several approaches to the problem have already been described; most of them use some kind of sensor to establish the position and speed of the contacts in real time, whereas in our approach, the position and speed of the moving armature and contacts are calculated by using only the current and voltage values of the contactor coil as control inputs. A fuzzy controller takes as input the position and velocity of the armature and provides as output an intensity set point that controls the velocity of the closure of the contacts. Furthermore, we have developed a low-cost electronic module that implements the control system and integrates it in the contactor. The module eliminates the bounces completely and thus prevents the contacts from repeatedly making and breaking the circuit. View full abstract»

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  • Distributed Multipole Model for Design of Permanent-Magnet-Based Actuators

    Publication Year: 2007 , Page(s): 3904 - 3913
    Cited by:  Papers (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1265 KB) |  | HTML iconHTML  

    This paper presents a general method for deriving a closed-form solution for precise calculation of the magnetic field around a permanent magnet (PM) or an electromagnet (EM). The method, referred here as distributed multipole (DMP) modeling, inherits many advantages of the dipole model originally conceptualized in the context of physics, but provides an effective means to account for the shape and magnetization of the physical magnet. Three examples are given to illustrate the procedure of developing a DMP model, which derives an appropriate set of distributed dipoles from a limited set of known field points, for a general cylindrical PM, a customized PM, and a multilayer coil. The DMP modeling method has been validated by comparing simulated fields and calculated forces against data obtained experimentally and numerically; the comparisons show excellent agreement. Finally, we illustrate how the closed-form DMP models can offer an inexpensive means to visualize the effect of the EM fields on the leakage and unexpected flux paths, which have significant influences on the magnetic torque of a spherical motor. View full abstract»

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  • Multiobjective Optimization of Parallel Cable Layout

    Publication Year: 2007 , Page(s): 3914 - 3920
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    We have applied a multiobjective combinatorial optimization (MOCO) based on a vector immune system (VIS) algorithm to determine the optimal sequence of parallel cables in a multiconductor three-phase system. We build the objective function in a way that minimizes the magnetic stray field and the current unbalance of a bunch of rectilinear power cables. Our principal aim is to extend and verify the ability of the VIS algorithm to solve combinatorial problems represented by nonlinear objectives that are not usually solved in MOCO problems. View full abstract»

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  • Quasi-Reduced-State Soft-Output Viterbi Detector for Magnetic Recording Read Channel

    Publication Year: 2007 , Page(s): 3921 - 3924
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    Reduced-state trellis detection with decision feedback is widely used to reduce the energy consumption of trellis detectors, particularly for soft-output trellis detectors that are energy-hungry by nature. However, the decision feedback tends to increase the circuit critical path and, more important, makes it difficult to apply some well-proven high-speed trellis detector design techniques such as bit-level pipelining. This paper presents a method, referred to as quasi-reduced-state trellis detection, to tackle such speed bottlenecks. The basic idea is to simply obviate the use of decision feedback by mapping only the data storage block of the trellis detector onto a reduced-state trellis and keeping the trellis state metric computation on the original full-state trellis. This makes sense because the data storage block tends to dominate the overall energy consumption while the decision feedback is due to the reduced-state trellis metric computation. Therefore, it is intuitive that such quasi-reduced-state detectors may largely maintain the energy saving potentials of reduced-state trellis detection without being subject to decision-feedback-induced speed bottlenecks. We demonstrated the effectiveness of this proposed design method by using soft-output Viterbi algorithm (SOVA) detection for a magnetic recording read channel as a test vehicle. View full abstract»

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  • Improved Data Recovery from Patterned Media With Inherent Jitter Noise Using Low-Density Parity-Check Codes

    Publication Year: 2007 , Page(s): 3925 - 3929
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    Patterned magnetic media promises areal densities in excess of 1 Tbit/in2 for data storage. However, current imperfect patterning techniques result in a variation in the dimensions and distribution of the fabricated islands. As a result, this variation introduces jitter in the replay waveform that makes data recovery difficult. In this paper, we investigate the use of low-density parity-check (LDPC) codes and iterative decoding for mitigating the effects of lithography jitter and improving the read channel performance in patterned media storage systems. In addition, we show that the adoption of LDPC coding techniques permits an increase in the data storage capability of the medium to approximately 1.6 Tbit/in2 with acceptable bit-error-rate performance. View full abstract»

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  • Exchange-Coupled IrMn/CoFe Mulitlayers for RF-Integrated Inductors

    Publication Year: 2007 , Page(s): 3930 - 3932
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (245 KB) |  | HTML iconHTML  

    The high-frequency characteristics of the RF integrated inductors with antiferromagnetic/ferromagnetic (AF/F) multilayers (MLs) are studied. Each AF layer is 8-nm IrMn and F is Co50Fe50 with a 200-nm splitting into N = 1 to 5 repeats of MLs. This exchange coupled {IrMn/CoFe(d nm)}N MLs are deposited on top of the two-port inductors with five-turn square spiral coils, a dimension of 100 mum times 100 mum and line/space of 5 mum/2 mum. The inductor surface and magnetic layer is separated by 1-mum-thick SiO2. The enhancement of inductance (DeltaL) is 20% compared to an air-core of the same coil size. The resonance peak gradually shifted to a higher frequency with increasing N, and reached at a maximum of 4.3 GHz when N = 5. This is in good agreement with our magnetic data which revealed that the anisotropy field (Hk) and ferromagnetic resonance frequency (fFMR) of {IrMn/CoFe(d nm)}N MLs are increased with increasing N. The quality factor, Q is improved by 6.8% at 1.5 GHz for the {IrMn/CoFe(40 nm)}N=5 integrated inductors compared to air-core inductors. View full abstract»

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  • Correction to: "Planes of Continuous-Wave Oscillations From an Electron Nanocontact Spin-Transfer Device" [May 07 1934-1940]

    Publication Year: 2007 , Page(s): 3933
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    In the above titled paper (ibid., vol. 43, no. 5, pp. 1934-1940, May 07), two errors were noted. The corrected information is presented here. View full abstract»

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  • Leading the field since 1884 [advertisement]

    Publication Year: 2007 , Page(s): 3934
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  • IEEE Magnetics Society & The IEEE Press call for books

    Publication Year: 2007 , Page(s): 3935
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  • Explore IEL IEEE's most comprehensive resource [advertisement]

    Publication Year: 2007 , Page(s): 3936
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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