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Magnetics, IEEE Transactions on

Issue 12 • Date Dec. 2007

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Displaying Results 1 - 18 of 18
  • [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): 4053
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  • In Memoriam

    Publication Year: 2007 , Page(s): 4054 - 4055
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  • Effect of Variable Biquadratic Exchange Coupling on the Magnetic Hysteresis of Uniaxial Antiferromagnetic Co/Ru/Co Films

    Publication Year: 2007 , Page(s): 4056 - 4059
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (157 KB) |  | HTML iconHTML  

    We investigated biquadratic exchange coupling strength in sputtered uniaxial antiferromagnetic Co/Ru/Co trilayers, which can be tuned by applying a magnetic field perpendicular to the sample surface during deposition. The perpendicular field induces a columnar grain structure that results in a perpendicular magnetic anisotropy for single Co layers. The perpendicular magnetic anisotropy is detected by combined magnetization and Brillouin light scattering measurements. In trilayers, increasing the perpendicular field during deposition results in a monotonic increase of the biquadratic exchange coupling strength, so these samples provide an experimental realization of the effect of variable biquadratic coupling strength on magnetic hysteresis behavior. The hard-axis remanence is a direct measure of biquadratic exchange coupling strength, which we demonstrated both by experiment and by a Stoner-Wohlfarth model that includes the relevant magnetic parameters. View full abstract»

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  • Soft Magnetic Properties of Obliquely Deposited Co–Zr–O Films

    Publication Year: 2007 , Page(s): 4060 - 4063
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1623 KB) |  | HTML iconHTML  

    We have studied obliquely sputtered Co-Zr-O films. We found that oblique deposition gives rise to the formation of columnar morphology and thus higher perpendicular magnetic anisotropy in the films, which finally results in the occurrence of stripe domains and degradation of soft magnetic properties. Applying substrate bias during Co-Zr-O film deposition gave some improvement in magnetic softness with small slope angles, but did not provide any improvement for large angles. Using a multilayer structure Co-Zr-O/ZrO2 effectively eliminates the columnar structure and helps the films regain favorable soft magnetic properties. View full abstract»

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  • Support Vector Regression for Measuring Electromagnetic Parameters of Magnetic Thin-Film Materials

    Publication Year: 2007 , Page(s): 4071 - 4075
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB) |  | HTML iconHTML  

    We propose a novel method for extracting the electromagnetic parameters (complex permittivity and permeability) of magnetic thin-film materials. The method extracts electromagnetic parameters of the magnetic thin films from effective electromagnetic parameters by using the supported vector machine (SVM). We validated the method in the frequency range of 1-8 GHz. The results show that the errors for both epsiv' and mu' are less than 0.5%, and the errors of both tan deltaepsiv and tan deltamu are less than 0.001. View full abstract»

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  • Multiscale Computations of Parameters of Power Transformer Windings at High Frequencies. Part II: Large-Scale Level

    Publication Year: 2007 , Page(s): 4076 - 4082
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1527 KB) |  | HTML iconHTML  

    In this part of the paper, we focus on implementation of a hierarchical multiscale approach for modeling high-frequency electromagnetic processes in power transformers. We present a large-scale 3D computer model for calculating magnetic fields in a transformer and evaluating effective parameters (inductance and resistance) of its windings and losses. The model accounts for complex, anisotropic, and frequency-dependent effective diamagnetic properties of the windings, which are obtained by solving small-scale 2D field problems as described in Part I of the paper. Results of the computations performed for a test transformer are analyzed in the frequency range 10 Hz-10 MHz. We discuss effects of windings conditions (open and short-circuited) and their location on the transformer core. View full abstract»

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  • Comparison of the Unbalanced Magnetic Pull Mitigation by the Parallel Paths in the Stator and Rotor Windings

    Publication Year: 2007 , Page(s): 4083 - 4088
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    An eccentric rotor creates an electromagnetic force between the rotor and stator of an electrical machine. This force tends to further increase the rotor eccentricity and may severely degrade the performance of the machine, causing acoustic noise, vibration, excessive wear of bearing, rotor and stator rubbing, and so forth. Parallel connections are known to be a simple yet effective remedy for the problems associated with rotor eccentricity. We have investigated two common types of electrical machines running with eccentric rotors. We examined operation over a wide whirling frequency range. We numerically evaluated and compared the effects of parallel connections in the stator and rotor windings on the eccentricity force. We found that the parallel stator windings can be more effective in mitigating the unbalanced magnetic pull than the rotor cage (or damper winding), which normally has many more parallel circuits. View full abstract»

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  • Switched Reluctance Motor Design Using Neural-Network Method With Static Finite-Element Simulation

    Publication Year: 2007 , Page(s): 4089 - 4095
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1572 KB) |  | HTML iconHTML  

    The paper describes a neural network method for optimal design of a switched reluctance motor (SRM). The approach maximizes average torque while minimizing torque ripple, considering mainly the stator and rotor geometry parameters. Before optimization takes place, an experimental validation of the SRM model, based on the finite-element method, is performed. The validation predicts average torque and torque ripple characteristics for several motor configurations while stator and rotor pole arcs are varied. The numerical results are highly nonlinear, and a function approximation of the data is therefore difficult to implement. We therefore interpolate the data by using a neural network based on a generalized radial basis function. The computed results allow us to search for optimum motor parameters. The optimum design was confirmed by numerical field solutions. View full abstract»

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  • A Linear Algorithm for Tracing Magnet Position and Orientation by Using Three-Axis Magnetic Sensors

    Publication Year: 2007 , Page(s): 4096 - 4101
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    For medical diagnoses and treatments, it is often desirable to wirelessly trace an object that moves inside the human body. A magnetic tracing technique suggested for such applications uses a small magnet as the excitation source, which does not require the power supply and connection wire. It provides good tracing accuracy and can be easily implemented. As the magnet moves, it establishes around the human body a static magnetic field, whose intensity is related to the magnet's 3-D position and 2-D orientation parameters. With magnetic sensors, these magnetic intensities can be detected in some predetermined spatial points, and the position and orientation parameters can be computed. Typically, a nonlinear optimization algorithm is applied to such a problem, but a linear algorithm is preferable for faster, more reliable computation, and lower complexity. In this paper, we propose a linear algorithm to determine the 5-D magnet's position and orientation parameters. With the data from five (or more) three-axis magnetic sensors, this algorithm results in a solution by the matrix and algebra computations. We applied this linear algorithm on the real localization system, and the results of simulations and real experiments show that satisfactory tracing accuracy can be achieved by using a sensor array with enough three-axis magnetic sensors. View full abstract»

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  • Innovative Three-Axial Actuator for High-Density Optical Drive

    Publication Year: 2007 , Page(s): 4102 - 4105
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (791 KB) |  | HTML iconHTML  

    As the density in optical data storage systems increases, a drive capable of tilt control thus becomes necessary in order to improve the tilt margin as the coma aberration is accordingly increased. In this paper, we propose an innovative three-axial actuator based on a traditional four-wire scheme with an additional pair of tilting magnets. The proposed coil-driven servo can independently compensate plusmn1 tilt degree associated with a torque variation of less than 5%. The driving forces of the focusing and tracking are kept constant while the tilt servo is activated. View full abstract»

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  • Study of Lithographically Defined Data Track and Servo Patterns

    Publication Year: 2007 , Page(s): 4106 - 4112
    Cited by:  Papers (8)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2102 KB) |  | HTML iconHTML  

    We report on fabrication of discrete tracks on perpendicular magnetic recording (PMR) media with an e-beam lithographical process. We studied the recording performance of the e-beam media on a spinstand in parallel with conventional PMR media. Discrete track media show significant reduction in adjacent track erasure (ATE). We studied and quantitatively measured the source of the ATE improvement, and developed a triple track geometrical model to calculate achievable track density for both discrete track recording (DTR) and continuous media. From the model, we identify two factors of DTR that contribute to reaching a higher TPI. Using the same fabrication technique, we also studied servo burst design and its playback waveform quality. At 250 ktpi, we compare DTR servo bursts with servo bursts written with a conventional method. DTR servo bursts show better edge definition, which can translate to better position error signal sensitivity and support higher TPI in the future.Discrete tracks are fabricated on conventional PMR media with an e-beam litho graphical process. The recording performance is studied on a spinstand in parallel with conventional PMR media. Discrete track media shows significant reduction in adjacent track erasure (ATE). The source of the ATE improvement is studied and quantitatively measured. A triple track geometrical model is developed to calculate achievable track density for both DTR and continuous media. From the model, we identify two factors of DTR, which contribute to reaching a higher TPI. Using the same fabrication technique, we also study servo burst design and its playback waveform quality. At 250 ktpi, we compare DTR servo bursts and servo bursts written with a conventional method. DTR servo bursts show better edge definition, which can translate to better PES signal sensitivity and support higher TPI in the future. View full abstract»

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  • Use of Low-Density Parity-Check Codes for Dominant Error Events Detection and k -Constraint Enforcement

    Publication Year: 2007 , Page(s): 4113 - 4116
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB) |  | HTML iconHTML  

    In this paper, we propose to leverage the simple and explicit parity checks inherent in low-density parity-check (LDPC) codes to detect dominant error events without code rate penalty. This is enabled by enforcing a very weak constraint on the LDPC code parity check matrix structure. Such a constraint can be readily satisfied by most structured LDPC codes reported in the open literature, such as quasi-cyclic (QC) LDPC codes. Moreover, this zero-redundancy dominant error events detection can be extended to handle the bit errors that occur when deliberate bit-flipping is used to enforce -constraints. We have demonstrated the effectiveness of the proposed method in computer simulations. View full abstract»

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  • Area-Efficient Min-Sum Decoder Design for High-Rate Quasi-Cyclic Low-Density Parity-Check Codes in Magnetic Recording

    Publication Year: 2007 , Page(s): 4117 - 4122
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    We report a silicon area efficient method for designing a quasi-cyclic (QC) low-density parity-check (LDPC) code decoder. Our design method is geared to magnetic recording that demands high code rate and very high decoding throughput under stringent silicon cost constraints. The key to designing the decoder is to transform the conventional formulation of the min-sum decoding algorithm in such a way that we can readily develop a hardware architecture with several desirable features: 1) silicon area saving potential inherent in the min-sum algorithm for high-rate codes can be fully exploited; 2) the decoder circuit critical path may be greatly reduced; and 3) check node processing and variable node processing can operate concurrently. For the purpose of demonstration, we designed application-specific integrated circuit decoders for four rate-8/9 regular-(4, 36) QC-LDPC codes that contain 512-byte, 1024-byte, 2048-byte, and 4096-byte user data per codeword, respectively. Synthesis results show that our design method can meet the beyond-2 Gb/s throughput requirement in future magnetic recording at minimal silicon area cost. View full abstract»

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  • 2007 Index IEEE Transactions on Magnetics Vol. 43

    Publication Year: 2007 , Page(s): 4123 - 4264
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  • IEEE Magnetics Society Information

    Publication Year: 2007 , Page(s): C3
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  • IEEE Transactions on Magnetics institutional listings

    Publication Year: 2007 , 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