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Magnetics, IEEE Transactions on

Issue 12 • Date Dec. 2010

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  • [Front cover]

    Publication Year: 2010 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2010 , Page(s): C2
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  • Table of contents

    Publication Year: 2010 , Page(s): 3965 - 3966
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  • Magnetic Composite Materials and Arbitrary B - H Relationships

    Publication Year: 2010 , Page(s): 3967 - 3972
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1007 KB) |  | HTML iconHTML  

    This theoretical study addresses fabricating composite conducting materials with an effective arbitrary B-H relationship in the quasi-static field approximation, exhibiting new magnetic properties. The experimental results demonstrate the possibility of having linear artificial structures with negative effective magnetic permeability. The equivalent circuital model confirms the theoretical and experimental analysis. In particular, following the circuital approach we show how to obtain linear and nonlinear materials that exhibit circular B-H relationships at specific frequencies. Results of a previous experimental analysis aimed at discussing the operative meaning of the measurement of magnetism in composite materials are reported for completeness together with a description of the new conjectured prototypes. Finally, we advance some preliminary discussion on the possibility of defining composite conducting materials that exhibit arbitrary B-H loci symmetrical with respect to the H-axis, for which it is possible to observe wave-like solutions for an electromagnetic field diffusing into the material. This merits further exploration. View full abstract»

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  • Composition Dependence of Structural and Magnetic Properties of Electrodeposited Co-Cu Films

    Publication Year: 2010 , Page(s): 3973 - 3977
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    The structural and magnetic properties of Co-Cu films were studied in terms of Co content in the films. The surface morphology of the films showed that the film with the lowest Co content (3 wt. %) had dendritic structures, whereas the surface of the film containing the highest amount of Co (61 wt. %) was more uniform with acicular shapes in some parts. X-ray diffraction patterns of the films showed that their crystal structure is a mixture of dominantly face-centered cubic (fcc) and hexagonal close-packed phases. At the lowest Co content, separate fcc (111) peaks appear, whereas the increase of Co content converts the peaks to be a single broad Co-Cu peak. The vibrating sample magnetometer measurements revealed that the saturation magnetization increases and coercivity decreases due to the decrease of the grain size caused by the increase of the Co content in the film. The structural and magnetic properties of Co-Cu films can be tailored, since these properties are directly related to the ratio of Co to Cu in the film. View full abstract»

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  • A Simple Way to Synthesize Superparamagnetic Iron Oxide Nanoparticles in Air Atmosphere: Iron Ion Concentration Effect

    Publication Year: 2010 , Page(s): 3978 - 3983
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1657 KB) |  | HTML iconHTML  

    We have synthesized iron oxide nanoparticles in air atmosphere by coprecipitation. The ratio of was fixed at 2/3. The total amount of iron ions in the solution was varied from 250 mmol to 12.5 mmol. X-ray diffraction (XRD) patterns showed the characteristic peaks of iron oxide phases. We observed that the crystallinity reduced and particle sizes calculated from XRD patterns decreased as the iron ion concentration in the solution decreased. Fourier transform infrared spectroscopy analysis exhibited the Fe-O vibration band at 560-580 confirming the iron oxide formation. The mean physical sizes obtained from a transmission electron microscope are around 8 nm. According to the magnetic measurements, all samples are superparamagnetic at room temperature showing an increase in saturation magnetization up to 63.71 emu/g. Magnetic sizes of the particles vary from 7.45 nm to 4.88 nm with the change of iron ion concentration. View full abstract»

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  • Use of Jiles–Atherton and Preisach Hysteresis Models for Inverse Feed-Forward Control

    Publication Year: 2010 , Page(s): 3984 - 3989
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (629 KB) |  | HTML iconHTML  

    Hysteresis effects hinder the accurate control of electromagnetic actuators and require auxiliary sensors for properly determining the hysteretic system state. The physics-based Jiles-Atherton and the phenomenological Preisach hysteresis models provide powerful means to describe the magnetic hysteresis and its inverse. In this paper, we consider both hysteresis models in the scalar form from the control points of view, with a primary objective of the sensorless inverse feed-forward control. The identification complexity, the runtime, and the space efficiency of the control-oriented implementation are analyzed and compared for both modeling approaches. Their control performance for an inverse hysteresis compensation is experimentally evaluated on a specific force-controlled electromagnet system. View full abstract»

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  • A General Vector Hysteresis Operator: Extension to the 3-D Case

    Publication Year: 2010 , Page(s): 3990 - 4000
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1088 KB) |  | HTML iconHTML  

    This paper deals with the mathematical definition of a general vector hysteresis operator in 3-D, as an extension of previous papers where the theory has been limited to the 2-D case. Although the paper is mainly focused on magnetic hysteresis, the definitions and the results reported can be applied to any general physical phenomenon that exhibits hysteresis. We show here the main general properties of the general hysteresis operator in 3-D. View full abstract»

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  • Effect of Anisotropy and Direction of Magnetization on Complex Permeability of Ferromagnetic Rectangular Thin Slabs

    Publication Year: 2010 , Page(s): 4001 - 4008
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (593 KB) |  | HTML iconHTML  

    Ultrasoft magnetic materials, such as amorphous, nanocrystalline, and polycrystalline alloys, have been successfully used for power electronic applications during recent years. However, enhancements are needed for the integration of power electronic features, which involves high power densities and operating frequencies up to a few megahertz. Complex permeability spectra, which are used to describe material behavior in these applications, depend mainly on domain-wall motions and coherent magnetization rotation mechanisms. In this paper, we present a model describing these mechanisms, in terms of magnetic anisotropies and domain structure of the material. To validate the model, we measured permeability spectra of polycrystalline Ni-Fe alloys under mechanical stress using a specific setup. These measurements are suitable for comparing the physical model according to different magnetoelastic anisotropies. Results are useful for correlating high-frequency magnetic behavior and the annealing process of materials. View full abstract»

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  • Ampere's Circuital 3-D Model for Noncuboidal Magnets

    Publication Year: 2010 , Page(s): 4009 - 4015
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (749 KB) |  | HTML iconHTML  

    Analytical equations describing the three-dimensional field of permanent magnets are attractive tools for the optimization of permanent-magnet based structures. The shape of the magnets determines to a high extent the type of solution. The objective of this research is to find the equations describing the field of a pyramidal frustum, based on the Biot-Savart law. We develop analytical equations describing the field of current carrying sheets. These equations make it possible to treat the field of any permanent-magnet shape with a uniform magnetization and flat surfaces. View full abstract»

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  • Convexity-Oriented Method for the Topology Optimization of Ferromagnetic Moving Parts in Electromagnetic Actuators Using Magnetic Energy

    Publication Year: 2010 , Page(s): 4016 - 4022
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (567 KB) |  | HTML iconHTML  

    When applied to the topology optimization of electromagnetic devices, gradient-based algorithms suffer from a lack of convexity. They usually converge to local minimizers and the obtained designs depend on the initial material distributions. This paper focuses on avoiding these local minimizers for the optimization of ferromagnetic moving parts in electromagnetic actuators. The proposed method intends to maximize the average reluctant force computed from the difference of magnetic energy between two positions of the ferromagnetic part. It relies on a problem relaxation: distinct design variables are defined to describe the ferromagnetic part in each position. Thanks to convexity-oriented constraints, the differences between the two obtained topologies are progressively reduced in order to converge towards the optimal design. The paper besides highlights sensitivity issues related to the high permeability of iron and recommends using a geometric mapping to guarantee a fast convergence. The efficiency of the method is underlined for the design of the rotor of a switched reluctant actuator. The method succeeds in avoiding local minimizers and producing efficient topologies. The method is then combined with another method dedicated to the design of parts composed of iron and coils in order to realize the global optimization of the actuator. View full abstract»

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  • A New Tracking System for Three Magnetic Objectives

    Publication Year: 2010 , Page(s): 4023 - 4029
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB) |  | HTML iconHTML  

    We have implemented a new noninvasive multiobjective tracking system, which can be used for localization of an endoscope and monitoring of heart valve prostheses and gastrointestinal transit of solid oral dosage forms or nutrients. The marker is modeled as a magnetic dipole, and the magnetic field at some point is regarded as summation of those from three dipoles. By minimizing the squared errors of magnetic field values between measurements and calculation using a hybrid of the particle swarm optimization (PSO) algorithm and the clone algorithm, an iterative result can be obtained, which is taken as the initial guess of the Levenberg-Marquardt (L-M) optimization method, and the first point can be determined. Subsequently, the previous computed point is used as the next initial guess of L-M algorithm, and the successive points are calculated. The tracking results demonstrate that the average position error for three objectives is 3.7 mm and the average orientation error is 1.8 when the objectives move randomly in the space surrounded by the sensor array. View full abstract»

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  • Novel High-Speed Electromagnetic Actuator With Permanent-Magnet Shielding for High-Pressure Applications

    Publication Year: 2010 , Page(s): 4030 - 4033
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (277 KB) |  | HTML iconHTML  

    We present a novel moving-iron, high-pressure, high-speed electromagnetic actuator that utilizes permanent-magnet (PM) shielding for increasing air-gap flux. We analyze its static and dynamic characteristics by using the finite-element method, taking into account the nonlinear characteristics and the eddy-current loss of the magnetic material. The experimental and simulated results agree well and show that the actuator has a displacement of 0.6 mm, closing time of 2.24 ms, and opening time of 7.78 ms without latching force. View full abstract»

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  • A Novel 3-DOF Axial Hybrid Magnetic Bearing

    Publication Year: 2010 , Page(s): 4034 - 4045
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1654 KB) |  | HTML iconHTML  

    In this paper, we propose a novel structure of permanent-magnet-biased axial hybrid magnetic bearing. It has four segments of poles to control three degrees of freedom (3-DOF). Based on the inner and outer air gaps in conventional axial magnetic bearings, a novel air gap, called the subsidiary air gap, is constructed between the permanent magnet and the stator poles. This air gap separates the bias flux paths from the control flux paths. As a result, lower power loss of the axial magnetic bearing can be achieved due to lower magnetic reluctance of the control flux paths. Furthermore, by means of the equivalent magnetic circuit method and the 3-D finite-element method (FEM), we analyze and model the 3-DOF axial hybrid magnetic bearing. Experimental results show that the presented axial magnetic bearing has good control performance and little coupling among X, Y, and Z directions. However, the rotational power loss will be large at high speed because of the alternating flux density in the thrust plate produced by four segments of stator poles. Therefore, we propose a novel stator, named the parallel-slot stator, and novel thrust plate to reduce the rotational power loss effectively, which is assembled by DT4 and nanocrystalline materials. Meanwhile, we have designed and assembled an axial hybrid magnetic bearing prototype with the novel stator and thrust plate, which is applied in the five-degrees-of-freedom reaction flywheel system with angular momentum of 15 Nms at 5000 r/min. It is validated by the experimental results. View full abstract»

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  • Effect of Model Accuracy on the Result of Computed Current Densities in the Simulation of Transcranial Magnetic Stimulation

    Publication Year: 2010 , Page(s): 4046 - 4051
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB) |  | HTML iconHTML  

    In this paper, we study the effects of model complexity on the accuracy of the results in the computer simulation of transcranial magnetic stimulation (TMS). The method has been extensively used in the last decade as a noninvasive technique to excite neurons in the brain by inducing weak electric currents in the tissue and proved to be a very promising alternative for currently invasive treatments in Parkinson's and Alzheimer's diseases. A detailed 3-D model of a human head has been developed by combining individual patient-based brain images and the public domain Visible Human data consisting of brain white/gray matter, CSF, skull, and muscles. The finite-element method (low-frequency Ansoft Maxwell 3D package) is used to simulate the interaction of time-varying magnetic fields with brain tissues and to compute the densities of induced currents in different areas. Models with different levels of tissue separation have been developed and tested under the same condition to investigate the effects of model complexity on the distribution of fields and induced currents inside different tissues. View full abstract»

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  • Design and Optimization of a Novel Bored Biplanar Permanent-Magnet Assembly for Hybrid Magnetic Resonance Imaging Systems

    Publication Year: 2010 , Page(s): 4052 - 4058
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    We present a novel design for a biplanar permanent-magnet assembly suitable for use in hybrid magnetic resonance imaging (MRI) systems. The key feature of our design is a large cylindrical hole that is longitudinally bored through the entire magnet assembly. The presence of the bore permits the potential inclusion of additional peripheral devices within or near the magnet structure that may benefit from being placed along, or oriented parallel to, the main magnetic field. In particular, the magnet assembly can be considered for use in an integrated system consisting of a 6 MV medical linear accelerator (linac) coupled to an MRI system for state-of-the-art real-time image-guided adaptive radiotherapy. We use magnetic field calculations based on the finite-element method (FEM) to quantify the detrimental effects of the bore on the field homogeneity in the imaging volume for pole-piece designs found commonly in industry. We then demonstrate that shape optimization of the pole pieces yields novel pole designs that lead to suitable levels of field homogeneity. We examined the resultant magnetic field within the bore for the optimized design and found that it has maximum field homogeneity. View full abstract»

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  • Recording at Large Write Currents on Obliquely Evaporated Medium and Application to a Multilevel Recording Scheme

    Publication Year: 2010 , Page(s): 4059 - 4065
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (915 KB) |  | HTML iconHTML  

    We have studied the recording process of an obliquely evaporated Co-CoO medium. The experimental readback waveforms and the spin-SEM images of the recorded magnetization reveal an interesting magnetization process upon increasing the write current in one of the two recording directions. With larger write currents, isolated readback pulses drastically change their shape and the remanent magnetization of the written domains decreases. We qualitatively reproduce this behavior using simple write models that include the three-dimensional (3-D) granular nature of the medium and a distribution of anisotropy axes for the evaporated Co grains. Based on these results, we propose a recording scheme in which a patterned multilevel tilted recording medium is used advantageously for 3-D magnetic recording. View full abstract»

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  • Line-Start Permanent-Magnet Motors: Significant Improvements in Starting Torque, Synchronization, and Steady-State Performance

    Publication Year: 2010 , Page(s): 4066 - 4072
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1466 KB) |  | HTML iconHTML  

    We present a new scheme to improve the starting torque and synchronization capability of line-start permanent-magnet motors based on pole changing winding. Pole changing at start-up neutralizes the magnetic influence of permanent magnets and, therefore, leads to the elimination of braking and pulsating torques, and enhances the starting torque. Our scheme also solves the synchronization problem. We used finite-element analysis to validate the scheme. The simulation results show that the method leads to a high starting torque, good synchronization, and excellent steady-state performance. View full abstract»

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  • Iron and Magnet Losses and Torque Calculation of Interior Permanent Magnet Synchronous Machines Using Magnetic Equivalent Circuit

    Publication Year: 2010 , Page(s): 4073 - 4080
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (812 KB) |  | HTML iconHTML  

    We present a faster and simpler approach for the calculation of iron and magnet losses and torque of an interior permanent-magnet synchronous machine (IPMSM) than finite-element methods (FEM). It uses a magnetic equivalent circuit (MEC) based on large elements and takes into account magnetic saturation and magnet eddy currents. The machine is represented by nonlinear and constant reluctance elements and flux sources. Solution of the nonlinear magnetic circuit is obtained by an iterative method. The results allow the calculation of losses and torque of the machine. Due to the approximations used in the formulation of the MEC, this method is less accurate but faster than nonlinear transient magnetic FEM, and is more useful for the comparison of different machine designs during design optimization. View full abstract»

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  • A Comprehensive Analytical Mathematic Model for Permanent-Magnet Synchronous Machines Incorporating Structural and Saturation Saliencies

    Publication Year: 2010 , Page(s): 4081 - 4091
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1283 KB) |  | HTML iconHTML  

    We introduce a new method to model permanent-magnet synchronous machines (PMSMs) with saliencies due to the salient structure and magnetic saturation. We define two parameters to indicate these saliencies, i.e., the structural saliency ratio and the saturation saliency ratio . To verify the nonlinear model, we tested a real PMSM and numerically simulated it. The nonlinear inductance matrix is deduced and expressed by a nonlinear function regressed from the experimental data. The simulation and experimental results agree well with each other. View full abstract»

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  • Optimum Design of Tubular Permanent-Magnet Motors for Thrust Characteristics Improvement by Combined Taguchi–Neural Network Approach

    Publication Year: 2010 , Page(s): 4092 - 4100
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1222 KB) |  | HTML iconHTML  

    Although tubular permanent-magnet motors have advantages such as remarkable force capability and high efficiency due to lack of end winding, they suffer from high thrust force ripple. This paper presents the use of Taguchi method and artificial neural network (ANN) for shape optimization of axially magnetized tubular linear permanent-magnet (TLPM) motors. A multiobjective design optimization is presented to improve force ripple, developed thrust, and permanent-magnet volume simultaneously. The iron pole-piece slotting technique is used and its design parameters are optimized to minimize the motor's force pulsation. To obtain optimal configuration using this technique, four design variables are selected and their approximate optimum values are determined by the Taguchi method using analysis of means (ANOM). In the next step, two more influential parameters are selected by analysis of variance (ANOVA) and their accurate optimum values are obtained by a trained ANN. Finite-element analysis (FEA) is used to appraise the performance of the motor in different experiments of the Taguchi method and for training the ANN. The results show that force pulsation of the optimized motor is greatly reduced while there is small drop in the motor thrust. View full abstract»

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  • Optimized Design Considering the Mass Influence of an Axial Flux Permanent-Magnet Synchronous Generator With Concentrated Pole Windings

    Publication Year: 2010 , Page(s): 4101 - 4107
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (791 KB) |  | HTML iconHTML  

    In this paper, the efficiency optimization of an axial flux permanent-magnet synchronous generator with concentrated pole windings is examined for a 3.6 kW/2000 rpm combined heat and power application. Because the efficiency of the machine is important, specific measures are taken in order to reduce losses in the machine: thin laminated grain oriented material in the teeth, concentrated pole windings, and segmented magnets. A study of the influence of a limited set of geometry parameters on the efficiency of this type of machine is done, using both analytical and finite-element methods. In the analytical as well as in the finite-element model, the inherent 3-D geometry of the axial flux machine is approximated by multiple 2-D models at different radii in circumferential direction. Afterwards, the influence of mass on the optimal values of the geometry parameters and the efficiency is considered, and it is found that mass can be seriously decreased with only a small reduction in efficiency. Finally, the results of both methods are compared with measurements on a prototype to evaluate their validity. View full abstract»

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  • Reduced-State Bahl–Cocke–Jalinek–Raviv Detector for Patterned Media Storage

    Publication Year: 2010 , Page(s): 4108 - 4110
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (355 KB) |  | HTML iconHTML  

    Bit-patterned media (BPM) is a promising candidate for future high-capacity magnetic storage. The inter-track interference (ITI) in BPM has been taken into account by the “multiple islands per read head” model. However, the complexity of the symbol-based detection for this model is too high for practical use. To reduce complexity, we propose to use the reduced-state Bahl-Cocke-Jelinek-Raviv (BCJR) detection algorithm for such a two-dimensional model. We compare the computational complexity of the proposed reduced-state detector to that of the full-state BCJR detector. Simulation results show that the proposed reduced-state BCJR detector can approach the optimal performance by 0.5 dB while significantly reducing the detector complexity. View full abstract»

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  • Scitopia.org [advertisement]

    Publication Year: 2010 , Page(s): 4111
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  • IEEE Magnetics Letters

    Publication Year: 2010 , Page(s): 4112
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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