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Magnetics, IEEE Transactions on

Issue 1 • Date Jan. 2012

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  • [Front cover]

    Publication Year: 2012 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2012 , Page(s): C2
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  • Table of contents

    Publication Year: 2012 , Page(s): 1 - 2
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  • IEEE Magnetics Society Distinguished Lecturers for 2012

    Publication Year: 2012 , Page(s): 3 - 6
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  • Correction of Order Parameter Calculations for FePt Perpendicular Thin Films

    Publication Year: 2012 , Page(s): 7 - 12
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (598 KB) |  | HTML iconHTML  

    The order parameter of FePt thin films plays an essential role in determining such diverse materials properties as magneto-crystalline anisotropy, magnetic coercivity and magnetic recording density. Typically, the order parameter for a bulk material is obtained by measuring the X-ray integrated intensity ratio of a super lattice peak to a fundamental peak and comparing this ratio to a theoretical value which has been calculated for a fully ordered sample. In this work, we present an analysis of the order parameter calculation in FePt L10 thin films taking into account the geometric features of the X-ray diffractometer, the crystallographic texture of FePt films, and the finite thickness of the films. The theoretical ratio of the (001) super lattice peak of FePt and the (002) fundamental peak of FePt is calculated as a function of the full width half maximum (FWHM) diffraction peaks from film and thickness for FePt thin films with perpendicular texture. A reliable order parameter calculation equation for Fe50Pt50 fiber textured perpendicular recording media is established. View full abstract»

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  • Localization of Electromagnetic Force Based on Material Models

    Publication Year: 2012 , Page(s): 13 - 17
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB) |  | HTML iconHTML  

    Various candidates are known for electromagnetic stress in material media that all coincide in free space with the Maxwell's stress tensor. Although the situation provides various total force computation methods it leaves ambiguous the concept of electromagnetic force density. Instead of considering electromagnetic force per unit of volume we restrict the localization to subvolumes of material bodies. This way classical dipole models for the basic material elements yields uniquely defined local electromagnetic force. The approach is demonstrated by computing the magnetic force on a ferromagnetic body in contact with a permanent magnet. View full abstract»

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  • Stress-Induced Eddy Currents in Magnetostrictive Energy Harvesting Devices

    Publication Year: 2012 , Page(s): 18 - 25
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (765 KB) |  | HTML iconHTML  

    The paper aims to provide a more accurate analysis of a magnetostrictive energy harvesting device by proposing a FEM model which, assuming a realistic nonlinear characteristic of the material, is able to describe the harvesting phenomena in presence of the eddy currents induced by the Villari effect. The study is focused on the investigation of the influence of those parameters, such as pre-stress and bias, on the field dynamics and, consequently, on the eddy currents loss phenomena which cannot be disregarded if a reliable prediction of the global performances of these devices is required. The numerical results are computed by considering a compressive stress-driven vibration source and show spatial profiles of the fields, losses, and recovered powers in different operating conditions. Comparisons with the linear model are also provided. View full abstract»

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  • Shape Effect of Magnetic Source on Stabilizing Range of Vertical Diamagnetic Levitation

    Publication Year: 2012 , Page(s): 26 - 30
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    This paper presents the results of a study on the shape effect of magnetic sources formed by standard coil and ring magnet elements on vertical diamagnetic levitation. The maximum stabilizing range, Dmax, of a permanent-magnet floater levitated with the assistance of two diamagnetic graphite plates and powered with magnetic sources of different shapes was measured experimentally. The results were found to be well-correlated with theoretical data. The effectiveness of a shaped field source was determined by comparing its Dmax to that of a single standard coil equivalent with the same total thickness, turns, and applied current. For the permanent magnetic sources, the comparison was to a single ring magnet of the same total thickness, volume, and residual flux. The results indicate that a cone-shaped source of either electromagnet or permanent magnet has positive effects. Theoretical analyses suggest that acquiring a levitation position farther from the magnetic source and a smaller magnitude in B'' are significant in obtaining a larger stabilizing range. View full abstract»

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  • Augmentation of Propulsion Based on Coil Array Commutation for Magnetically Levitated Stage

    Publication Year: 2012 , Page(s): 31 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB) |  | HTML iconHTML  

    This paper focuses on augmenting the propulsion via commutation of coil array for the long-stroke magnetically levitated stage with moving coils, whose mechatronics structure have been defined. The used commutation of coil array is based on the analytical force/torque-decomposing model of the stage and it is characterized by bounding the coil currents. Through this current-bounded commutation, the 1-norm of commutated coil current vector is increased so that the propulsion can be augmented, and simultaneously the infinite norm of commutated coil current vector is limited so that the amplitudes of commutated coil currents are not beyond the capacity of selected coil power amplifiers. By the investigation example of a long-stroke magnetically levitated stage with moving coils, it is theoretically verified that the propulsion (acceleration) can be augmented by 125% as well as the commutated coil currents can be kept within the capacity of selected coil power amplifiers, 3 A. The study results indicate that the propulsion of a magnetically levitated stage can be augmented via current-bounded commutation of coil array rather than via reconfiguring the mechatronics structure of stage or reselecting coil power amplifiers of larger capacity. View full abstract»

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  • Investigation of Axial Carrying Capacity of Radial Hybrid Magnetic Bearing

    Publication Year: 2012 , Page(s): 38 - 46
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB) |  | HTML iconHTML  

    This paper investigates the axial carrying capacity of a new radial hybrid magnetic bearing (RHMB) using experimental, finite element, and magnetic circuit methods. The thrust bearing of traditional structures is not included because an axial resilience is generated by this new RHMB when the rotor is axially displaced. The relationship between axial resilience and displacement is tested, from which the axial passive stability stiffness is derived. The passive stability stiffness linearly decreases with increased displacement. Based on the 2-D and 3-D finite element models of RHMB established with AYSYS software, the axial resilience is calculated and compared with the experimental results, which shows that the numerical results are fully consistent with the experimental ones. The influence of structural dimensions to the axial resilience, including air gap length, permanent magnet sectional area and height, and magnetic pole board height, are analyzed in detail based on the 2-D model. The formula to calculate the axial resilience suitable for different lengths of air gap is deduced by the magnetic circuit method. Theoretical results calculated by this formula are in good agreement with the experimental and numerical results. The conclusions are helpful in designing and controlling RHMB. View full abstract»

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  • Modified Solenoid Coil That Efficiently Produces High Amplitude AC Magnetic Fields With Enhanced Uniformity for Biomedical Applications

    Publication Year: 2012 , Page(s): 47 - 52
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (705 KB) |  | HTML iconHTML  

    In this paper, we describe a modified solenoid coil that efficiently generates high amplitude alternating magnetic fields (AMF) having field uniformity (≤10%) within a 125-cm3 volume of interest. Two-dimensional finite element analysis (2D-FEA) was used to design a coil generating a targeted peak AMF amplitude along the coil axis of ~ 100 kA/m (peak-to-peak) at a frequency of 150 kHz while maintaining field uniformity to >; 90% of peak for a specified volume. This field uniformity was realized by forming the turns from cylindrical sections of copper plate and by adding flux concentrating rings to both ends of the coil. Following construction, the field profile along the axes of the coil was measured. An axial peak field value of 95.8 ± 0.4 kA/m was measured with 650 V applied to the coil and was consistent with the calculated results. The region of axial field uniformity, defined as the distance over which field ≥ 90% of peak, was also consistent with the simulated results. We describe the utility of such a device for calorimetric measurement of nanoparticle heating for cancer therapy and for magnetic fluid hyperthermia in small animal models of human cancer. View full abstract»

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  • The Spatial and Temporal Distortion of Magnetic Fields Applied Inside a Magnetically Shielded Room

    Publication Year: 2012 , Page(s): 53 - 61
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    In the context of biomagnetism, a magnetically shielded room (MSR) is designed for shielding against external magnetic fields. Recently, several applications, such as combined structural magnetic resonance imaging (MRI) and functional magnetoencephalography (MEG), have emerged that require applying relatively strong magnetic fields inside the MSR. These magnetic fields induce eddy currents and magnetize the MSR walls that are made of materials with high permeability and conductivity. These eddy currents and magnetization generate secondary magnetic fields inside the room that disturb, e.g., combined MEG-MRI by affecting sample spins and by exceeding the available dynamic range of the magnetic field sensors. In this work, static and dynamic magnetic fields applied inside an MSR are studied both theoretically and experimentally. Using a spherical model, analytical expressions are derived for the amplitudes and time constants of the various secondary magnetic field modes. These predictions are validated by comparison with experimental measurements in a rectangular MSR. The results of this study facilitate, e.g., the design of coils compatible with an MSR; a self-shielded coil is presented that decreases the secondary magnetic fields to a small fraction. View full abstract»

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  • An Efficient Semianalytic Computation Method of Magnetic Field for a Circular Coil With Rectangular Cross Section

    Publication Year: 2012 , Page(s): 62 - 68
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB) |  | HTML iconHTML  

    A semianalytic formula for calculating the magnetic field produced by a circular coil with rectangular cross section in air is proposed. In the formula, the coil is approximated as a series of circular rings with small cross sectional area, of which the current density can be considered as constant. In order to simplify the calculation of the magnetic field, the translation transformation and scaling transformation are introduced. Furthermore, all the possible singular cases, in the expressions, are treated properly. Therefore, with the help of one-dimensional Gauss-Legendre quadrature, the magnetic field at any points in space produced by current-carrying circular coil, especially inside the coil, can be calculated very easily. View full abstract»

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  • Magnetic Force Between Inclined Circular Filaments Placed in Any Desired Position

    Publication Year: 2012 , Page(s): 69 - 80
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (794 KB) |  | HTML iconHTML  

    This paper presents new general formulas for calculating the magnetic force between inclined circular filaments placed in any desired position. We use two approaches to calculate the magnetic force, one based on Biot-Savart law and another based on the mutual inductance between these coils. All mathematical procedures are completely described to define coil positions that lead to relatively easy method for calculating the magnetic force between inclined circular filaments in any desired position. Two formulas obtained by the simple integration of different expressions in terms of complete elliptic integrals of the first and second kind give the same numerical results. The presented methods are understandable, numerically suitable and easy applicable for engineers and physicists. We validated the new formulas through a series of examples, which are presented here. View full abstract»

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  • Exact solutions for the mutual inductance of circular coils and elliptic coils

    Publication Year: 2012 , Page(s): 81 - 94
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (775 KB) |  | HTML iconHTML  

    An exact solution is presented for the mutual inductance between general noncoaxial thin circular and elliptic coils with parallel axes. The thin coil solution is given as an angular integral of an elliptic integral expression. In addition, for the coaxial case, an exact solution is given for the mutual inductance of a thick circular coil and a thick elliptic coil. The elliptic coil is such that the coil thickness is the same along both elliptic semi-axes. The thick coil solution is given as an integral of an expression involving Bessel and Struve functions. Extensive numerical results for sample geometries are given for both solutions, which are cross checked against each other in the limit as the thick coils become thin. View full abstract»

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  • General 2-D Steady-State Force and Power Equations for a Traveling Time-Varying Magnetic Source Above a Conductive Plate

    Publication Year: 2012 , Page(s): 95 - 100
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (415 KB) |  | HTML iconHTML  

    Two-dimensional (2-D) force and power loss equations are derived for the case when an arbitrary magnetic source is moving and/or rotating above a conductive plate composed of linear material. The problem is formulated using both the magnetic vector and scalar potential. In order to compute the forces and power loss due to the induced eddy currents, only the magnitude of the field along the surface of the conductive plate needs to be provided. The equations are validated by comparing them with a 2-D finite-element model. View full abstract»

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  • Aerodynamic Pressure Fluctuations Associated With Flow-Induced Vibration of the Head Gimbals Assembly Inside a Hard Disk Drive

    Publication Year: 2012 , Page(s): 101 - 106
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (347 KB) |  | HTML iconHTML  

    This paper presents an experimental investigation and numerical simulation on the spectrum-spatial characteristics of aerodynamic pressure fluctuations around the head gimbals assembly (HGA) in a working hard disk drive (HDD). The pressure fluctuations are measured through tiny holes on the HDD top cover above the HGA. The positioning error signal and servo system sensitivity in the working HDD are measured as well to evaluate the slider off-track vibration. Comparisons between the spectra of pressure fluctuations and the slider off-track vibration show that, the pressure fluctuations around the HGA are highly associated with the slider off-track vibration in terms of principal peaks in the spectra, especially at 1.83 kHz and 2.54 kHz. The results also show that the spatial coherence of pressure fluctuation around the HGA remains high at frequencies around the principal peaks in the spectra, which has been further confirmed by the numerical simulation based on a two-dimensional large eddy simulation model. It is concluded that the flow-induced HGA vibrations in an HDD can be detected and evaluated through the pressure fluctuations by a sensor around the HGA. View full abstract»

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  • Analytical Model for Predicting Magnet Loss of Surface-Mounted Permanent Magnet Machines Accounting for Slotting Effect and Load

    Publication Year: 2012 , Page(s): 107 - 117
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (703 KB) |  | HTML iconHTML  

    Based on the subdomain field model accounting for tooth-tips, the eddy current losses in magnets are calculated for surface-mounted permanent magnet machines. The contributions of both self action of each harmonic and mutual interaction between field harmonics of different orders to magnet loss are accounted for in the developed model. It allows for predicting magnet losses due to the open-circuit, armature reaction and load fields. By using the model, the influence of the slots, tooth-tips, tooth body shape, and current angle on the magnet loss is studied and the mutual interaction between field harmonics of different order are analysed. Extensive finite element analysis demonstrates excellent accuracy of the developed analytical model. View full abstract»

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  • Heuristic Structural Optimization of the Permanent Magnets Used in a Surface Mounted Permanent-Magnet Synchronous Machine

    Publication Year: 2012 , Page(s): 118 - 127
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2034 KB) |  | HTML iconHTML  

    Structural optimization, as the process of finding an optimal material distribution of a machine part, is known from the mechanical engineering, but in the field of the design of electrical machines only few dedicated applications of that method have been reported yet. Most described applications are electromagnetic actuators. This report deals with the problem of finding an optimal structure of the permanent magnets used within a surface mounted permanent-magnet synchronous machine. In contrast to other reported methods, which use continuous models to describe the material properties with a postponed homogenization process, this paper will present a possible solution to the structural optimization problem by a simple heuristic search algorithm. For that purpose, the preselected design area is discretized with suitable quadrilateral cells. The material properties of each cell are set by a simple heuristic search algorithm, while the material properties are chosen from a discrete set of material properties. Therefore, the resulting problem is a discrete optimization problem. The finite-element method is used to solve the magnetic field equations and to gain information about the optimization performance index for each material distribution variant occurring during the optimization process. View full abstract»

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  • 3-D Formal Resolution of Maxwell Equations for the Computation of the No-Load Flux in an Axial Flux Permanent-Magnet Synchronous Machine

    Publication Year: 2012 , Page(s): 128 - 136
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (830 KB) |  | HTML iconHTML  

    This paper presents a 3-D analytical model of an axial flux permanent-magnet synchronous machine, based on formal resolution of Maxwell equations. This method requires much less computation time than conventional 3-D finite elements, and is therefore suitable for optimization purposes. In a first part, the mathematical procedure used to compute the machine no-load flux is described in detail. This method is 3-D, and then takes into account the radial edge effects of the machine, as well as the curvature effects by a resolution in cylindrical coordinates. Moreover, the originality of this method lies in the fact that it is totally analytical. The obtained results are verified using 3-D finite elements, and compared with simpler analytical models of axial flux machines, taken from the literature. This work puts in evidence the advantages of the proposed model. In particular, it is shown that the radial edge effects are important for a correct estimation of the no-load flux. On the contrary, the curvature effects are a second-order phenomenon. View full abstract»

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  • Evaluation of Rotor-End Factors in Solid-Rotor Induction Motors

    Publication Year: 2012 , Page(s): 137 - 142
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (489 KB) |  | HTML iconHTML  

    Rotor-end factors are dimensionless quantities used in designing the solid-rotor induction motors to approximate the effects of finite length. It is well known that there are a few analytic estimates of these factors available. With certain, generally acceptable accuracy these match most of the configurations of motors with uniform rotors, but are not adequate for those containing axial slits. In this work, an appropriate three-dimensional model is proposed to numerically evaluate the factors of the rotor-end effect for the uniform (unslitted) and the axially slitted rotors having slits through the whole length. For the two cases these factors are expressed via ratios taken between the rotor powers calculated in three- and two-dimensional systems of coordinates, and are expressed as functions of frequency. The rotor-end factors obtained in such a way are different for the unslitted and slitted rotors. A notable improvement of accuracy is obtained in comparison with the traditional methodology when the numerically evaluated end-factors are used in the two-dimensional circuit-driven frequency-domain finite-element model to determine the motor characteristics. View full abstract»

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  • Effect of Inclined Static Eccentricity Fault in Single Stator-Single Rotor Axial Flux Permanent Magnet Machines

    Publication Year: 2012 , Page(s): 143 - 149
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1242 KB) |  | HTML iconHTML  

    This paper studies the effects of static eccentricity on axial flux permanent-magnet machines (AFPMMs) using three-dimensional finite-element analysis (3-D FEA). Use of numerical modeling makes it possible to precisely study the eccentricity in these types of machines. The accuracy of the FEM model is validated using experimental measurement. To the best awareness of the authors, effects of static eccentricity in AFPMMs have not been studied before. Hence, a new definition for the static eccentricity factor (SEF) is presented and it is shown that the occurrence of static eccentricity is very high in these types of machines. A motor with different degrees of rotor eccentricity is simulated and the flux density distribution in the air gap and the total axial force between rotor and stator is obtained. In addition, unbalanced magnetic force (UMF) is calculated and it is mentioned that a steady torque is created by the forces. This study indicates that static eccentricity has noticeable effects on motor characteristics and can deteriorate the motor performances. View full abstract»

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  • IEEE magnetics letters the journal of your field

    Publication Year: 2012 , Page(s): 150
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  • Advertisement - Scitopia.org

    Publication Year: 2012 , Page(s): 151
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  • Advertisement - Explore IEL IEEE's most comprehensive resource

    Publication Year: 2012 , Page(s): 152
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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