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Magnetics, IEEE Transactions on

Issue 9 • Date Sept. 2008

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  • [Front cover]

    Publication Year: 2008 , Page(s): C1
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    Freely Available from IEEE
  • IEEE Transactions on Magnetics publication information

    Publication Year: 2008 , Page(s): C2
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  • Table of contents

    Publication Year: 2008 , Page(s): 2089 - 2090
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  • Combinatorial Screening of the BiDyYb Iron Garnet Material System for High Kerr Rotation Composition

    Publication Year: 2008 , Page(s): 2091 - 2094
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (474 KB) |  | HTML iconHTML  

    We investigated the (BixDyyYb3-x-y)Fe5O12 ternary combinatorial composition spread with the goal of finding new compositions with a large magneto-optical effect for possible use as magneto-optical storage materials. High-throughput magneto-optical characterization of the spread showed that the Dy0.6Yb0.5Bi1.9Fe5O12 composition has the largest Kerr effect in this ternary system. After annealing at 690degC for 1 h, a scaled-up thin-film sample of this composition has a remanent magnetization as high as 90% of its saturation magnetization, indicating a good storage application potential. View full abstract»

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  • Effects of Surface Abrasion on Magnetization of VITROVAC 6025Z Ribbons

    Publication Year: 2008 , Page(s): 2095 - 2099
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (181 KB) |  | HTML iconHTML  

    The effects of abrading with sandpaper the surface of VITROVAC 6025Z ribbons on the parameters of their M -H loops (the coercive field Hc , the position of the center C, etc.) have been investigated. The application of surface fields HP (generated by core currents) enabled us to single out the effects of surface domains (surface domain structure (SDS) pinning) and surface irregularities (intrinsic pinning) on domain wall (DW) pinning in abraded and unabraded ribbons. The abrasion enhances the intrinsic DW pinning (increases Hc) and strongly modifies the SDS pinning which shows up in specific variations of Hc and C with HP. In particular, the effect of HP on surface domain structure (SDS) pinning, which was symmetrical in unabraded ribbon becomes asymmetrical upon abrasion (i.e., different on opposite surfaces). A simple model for the influence of HP on magnetization processes in soft magnetic ribbons describes the observed variations of Hc and C with HP in both abraded and unabraded ribbons. The use of abrasion in order to tune the effects of oblique fields on M-H loops is briefly discussed. View full abstract»

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  • High Permeability and Low Loss Ni–Fe Composite Material for High-Frequency Applications

    Publication Year: 2008 , Page(s): 2100 - 2106
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1684 KB) |  | HTML iconHTML  

    A magnetic material with high permeability and low loss characteristics at high frequency is required for miniaturizing electronic components such as antennas. The key factors to keeping low magnetic loss are a high magnetic resonance frequency and the suppression of the eddy currents. We have fabricated a low-loss magnetic composite material by dispersing Ni 78Fe22 (permalloy) fine flakes in polymers; the thickness of the flakes was less than skin depth. The magnetic loss decreased with increased stirring time, and the minimum value occurred when the agglomerated particles decreased and most of the particles were deformed into flakes. Moreover, Zn5Ni75Fe20 composite material indicated high permeability when the flakes were oriented in the direction of sheets. The effect of wavelength shortening by permeability enhancement and the low loss characteristic were confirmed by experimental results of a rod antenna loaded with the developed magnetic composite material. View full abstract»

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  • Microstructure, Electrical, and Magnetic Properties of ZrO _{2} Added MnZn Ferrites

    Publication Year: 2008 , Page(s): 2107 - 2112
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB) |  | HTML iconHTML  

    We investigated the influence of ZrO2 on the microstructure and electromagnetic properties of MnZn ferrites by characterizing fracture surface micrographs, magnetic properties, and dc resistivity. Powders of Mn 0.68Zn 0.25Fe 2.07O 4 composition were prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350degC for 4 h in N2/O2 atmosphere with 4% oxygen. The results show that the lattice constant and average grain size increase with ZrO2 concentration, but excessive ZrO 2 concentration will result in exaggerated grain growth and porosity increase. The dc resistivity, activation energy, saturation magnetic flux density, and initial magnetic permeability increase monotonically when the ZrO2 concentration is not more than 0.04 wt% and then decrease with further increase of ZrO2 concentration. On the other hand, the porosity, drift mobility, resonance frequency, and core loss decrease initially and then increase with the increase of ZrO2 concentration. View full abstract»

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  • Generalization of the Classical Method for Calculating Dynamic Hysteresis Loops in Grain-Oriented Electrical Steels

    Publication Year: 2008 , Page(s): 2113 - 2126
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (889 KB) |  | HTML iconHTML  

    We have studied the ability of two one-dimensional (1-D) time-stepping models, both based on the concept of magnetic viscosity, to reproduce dynamic loops and losses in grain-oriented (GO) electrical steels under arbitrary magnetization regimes. We found that GO steels (0.3 mm thick) can be modeled quite accurately at magnetizing frequencies up to 200 Hz by a thin sheet representation, which is applied to a bulk material. At higher frequencies, acceptable results can be obtained through a finite-difference solver of a 1-D penetration equation whose applicability to GO steels can be explained in terms of domain wall bowing. Because of the inertial effect introduced by the magnetic viscosity, the average error in the loss prediction is reduced from 40% for the conventional classical method to 5% for the methods we studied. We demonstrated the accuracy of the models using two GO steels whose losses and B-H characteristics were measured by computer-controlled Epstein and single-sheet testers. View full abstract»

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  • Room-Temperature Giant Magnetoelectric Effect From Coils Cored With MnZn Ferrite

    Publication Year: 2008 , Page(s): 2127 - 2129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (522 KB) |  | HTML iconHTML  

    We have built coils with MnZn ferrite cores that demonstrate an appreciable giant magnetoelectric effect (GME). Their maximum magnetoelectric (ME) output is as high as 87 V/Oe at tens of kilohertz, which is remarkable for devices without any power supply. Our experimental and theoretical analyses suggest that the GME of the coils originates from LC resonances. Our results show a practical way to design ME devices such as passive high-frequency sensitive magnetic sensors. We have found as well that attention should be paid to LC resonance when performing ME spectral measurements. View full abstract»

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  • Micromagnetic Simulation of a Magnetic Film With Surface Roughness

    Publication Year: 2008 , Page(s): 2130 - 2133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (283 KB) |  | HTML iconHTML  

    We have simulated micromagnetically the static magnetic structure and magnetic spectrum of a magnetic film with surface roughness, using a finite stripe film model. We found that the rough surface can lead to a ripple magnetic structure, which results in increasing the damping factor of the film, and that the damping factor increases with the increase of the root-mean-square roughness. For a particular film with a given rough surface, the damping factor first decreases because of a decrease of the magnetic dispersion, then increases because of the surface-roughness-induced demagnetizing effect with increasing the external field. View full abstract»

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  • General Formulation for Magnetic Forces in Linear Materials and Permanent Magnets

    Publication Year: 2008 , Page(s): 2134 - 2140
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    A previous work described how a magneto-mechanical tensor can be obtained from the application of the virtual work principle to the energy density or co-energy density in any given media. This paper describes how the volume and surface force densities can be obtained from this tensor. Taking these force densities into account, we can calculate the total force over any given magnetic medium that is surrounded by any other magnetic medium. This represents a generalization of the classic Maxwell theorem. With this methodology, it is possible to calculate the surface forces in bodies in contact. We demonstrate this by showing the equivalence of the results obtained by this procedure and the equivalent source method and the Kelvin expression method. These methods could previously be applied only to bodies surrounded by air. We also show that this procedure is equivalent to other methods used to calculate the forces between linear magnetic materials (Korteweg-Helmholtz's tensor, ponderomotive force density). We have compared our method with results from continuum design sensitivity analysis, a method that allows for the calculation of global and local forces in magnetic media in contact . View full abstract»

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  • Spin Wave Magnetic NanoFabric: A New Approach to Spin-Based Logic Circuitry

    Publication Year: 2008 , Page(s): 2141 - 2152
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1060 KB) |  | HTML iconHTML  

    We describe a magnetic nanofabric, which may provide a route to building reconfigurable spin-based logic circuits compatible with conventional electron-based devices. A distinctive feature of magnetic nanofabric is that a bit of information is encoded into the phase of the spin wave signal. This makes it possible to transmit information without the use of electric current and to utilize wave interference for useful logic functionality. The basic elements include voltage-to-spin-wave and wave-to-voltage converters, spin waveguides, a spin wave modulator, and a magnetoelectric cell. We illustrate the performance of the basic elements by experimental data and the results of numerical modeling. The combination of the basic elements leads us to construct magnetic circuits for NOT and majority logic gates. Logic gates such as AND, OR, NAND, and NOR are shown as the combination of NOT and reconfigurable majority gates. Examples of computational architectures such as a multibit processor and a cellular nonlinear network are described. The main advantage of the proposed magnetic nanofabric is its ability to realize logic gates with fewer devices than in CMOS-based circuits. Potentially, the area of the elementary reconfigurable majority gate can be scaled down to 0.1 mum2. We also discuss the disadvantages and limitations of the magnetic nanofabric. View full abstract»

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  • Multimodel Optimization Based on the Response Surface of the Reduced FEM Simulation Model With Application to a PMSM

    Publication Year: 2008 , Page(s): 2153 - 2157
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    This paper presents an analytical method for improving the optimal design of electromagnetic devices obtained analytically. This method extracts the significant parameters by using the gradient of difference between the outputs of the analytical model and those obtained with a finite-element method. These parameters are then employed to build a response surface in a reduced dimension space by using the moving least square method. To assess its viability, we compared our method to another recent approach in the optimal design of a permanent-magnet synchronous motor. The results show our method's superiority in terms of improvement of the solution and approximation of the real objective function . View full abstract»

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  • Mitigation of Cogging Force in Axially Magnetized Tubular Permanent-Magnet Machines Using Iron Pole-Piece Slotting

    Publication Year: 2008 , Page(s): 2158 - 2162
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB) |  | HTML iconHTML  

    We present a method for reducing the cogging force in axially magnetized tubular permanent-magnet machines. The method consists of placing several similar slots on the iron pole-pieces. By choosing the appropriate positions of the pole-piece slots, specific harmonics of the cogging force can be eliminated, and, as a result, the cogging force may be greatly reduced. To obtain a general expression for the positions of the iron pole-piece slots, we use harmonic analysis with Fourier series. We demonstrate the validity of the cogging force reduction technique by finite-element analysis. View full abstract»

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  • Programmable Design of Magnet Shape for Permanent-Magnet Synchronous Motors With Sinusoidal Back EMF Waveforms

    Publication Year: 2008 , Page(s): 2163 - 2167
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB) |  | HTML iconHTML  

    The characteristics of a permanent-magnet synchronous motor (PMSM) are influenced greatly by the back-electromotive force waveforms in the motor, which are directly related to the magnet shape. We assume that the outer surface of a magnet in a PMSM can be modeled as one part of a cylinder. Using an ANSOFT model, we optimized the radius of the magnet with respect to number of poles, rotor size, and magnet thickness when the total harmonic distortion is below 1%. We then set up a lookup table using the optimization results so that the desired outer radius of a magnet of any new PMSM motor could be derived, subject to the parameter limits. We applied this method to some PMSM prototypes, and confirmed that the calculation results are substantially accurate. View full abstract»

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  • Design and Test of an Axial Flux Permanent-Magnet Machine With Field Control Capability

    Publication Year: 2008 , Page(s): 2168 - 2173
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (667 KB) |  | HTML iconHTML  

    We designed and tested a new axial flux permanent-magnet machine (AFPM) with field weakening capability. This paper provides a summary of key design features, optimization, and test results of an AFPM prototype. The proposed field weakening method is based on the control of the d-axis component of the armature reaction flux. The paper focuses on the air-gap flux control capability of the topology. View full abstract»

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  • Principle of Operation and Feature Investigation of a New Topology of Hybrid Excitation Synchronous Machine

    Publication Year: 2008 , Page(s): 2174 - 2180
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1389 KB) |  | HTML iconHTML  

    We present a new topology of hybrid excitation synchronous machine (HESM) and describe operational principles and features of the new configuration. Using the radial/axial distribution of the magnetic field, we develop an equivalent magnetic circuit model. We obtain magnetic flux, flux density, and induced voltage with various electrical magnetomotive forces by calculating the nonlinear magnetic circuit equation. We studied the Influence on the radial magnetic field of the axial magnetic field by 3-D finite-element method. The results are in good agreement with calculation by our magnetic circuit model. Our findings indicate that the air-gap flux density of a flux-concentrating HESM is high and the magnetic field in the air gap can be successfully regulated. Experimental results of 3 kVA prototype machine verify the feasibility of the structure and the correctness of our analysis. View full abstract»

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  • Analytical Force Determination in an Electromagnetic Actuator

    Publication Year: 2008 , Page(s): 2181 - 2185
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (275 KB) |  | HTML iconHTML  

    We present an original analytical determination of the force acting on the moving coil in an electromagnetic actuator. The actuator magnetic field is solved analytically by Schwarz-Christoffel (SC) mapping. The SC integral is solved analytically using the elliptic functions. We verified the results by finite-element methods. View full abstract»

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  • Modeling of a Switched Reluctance Machine Based on the Invertible Torque Function

    Publication Year: 2008 , Page(s): 2186 - 2194
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (490 KB) |  | HTML iconHTML  

    This paper presents a switched reluctance machine model based on an invertible expression representing the torque-phase current relationship. The model can be useful for real-time control in high-performance applications when the command current is derived from the torque command. The two angular functions that the model requires as input can easily be calculated from the known static torque-position characteristics for two currents. However, the paper also proposes the analytical models of the angular functions. The result is a geometry-based analytical model, with all parameters derived from machine geometry and material properties. Simulation and experimental results illustrate that the model provides very high accuracy. View full abstract»

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  • Demagnetization Assessment for Three-Phase Tubular Brushless Permanent-Magnet Machines

    Publication Year: 2008 , Page(s): 2195 - 2203
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1509 KB) |  | HTML iconHTML  

    We describe an analytical technique for assessing the risk of partial demagnetization in tubular permanent-magnet (PM) machines. The technique establishes analytical expressions for the open-circuit and armature reaction fields in the cylindrical coordinate system and superposes the fields in the permanent-magnet regions to determine the extent to which the magnets may be partially irreversibly demagnetized. We have applied the technique to a quasi-Halbach magnetized tubular PM machine equipped with a modular stator winding, and have validated the predictions by finite-element analysis. We found that partial demagnetization may occur even under an open-circuit operating condition when the machine is operating at high temperature. We propose alternative Halbach magnetization distributions that improve the demagnetization withstand capability. The analytical technique provides a computationally efficient tool for identifying regions that are prone to partial demagnetization and for assessing the consequences. It enables the risk of demagnetization to be fully assessed at the design stage so as to achieve a robust machine, particularly when operating in harsh environments. View full abstract»

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  • A Vibration-Based Condition Monitoring System for Switched Reluctance Machine Rotor Eccentricity Detection

    Publication Year: 2008 , Page(s): 2204 - 2214
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1977 KB) |  | HTML iconHTML  

    We propose a condition monitoring strategy for the detection of rotor eccentricity in switched reluctance machines. It uses vibration measurements and harmonic analysis to generate a Fourier series for the vibrations. Assessment of the change in key vibration components allows development of an eccentricity index that can give an indication of increasing eccentricity. The method discriminates between static and dynamic eccentricity. We have tested the method in simulation, using finite-element analysis, and verified it experimentally. Although mechanical resonance is an issue, a method of measurement over a number of speeds illustrates that it can be overcome. View full abstract»

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  • A Novel Parametric Model for AC Contactors

    Publication Year: 2008 , Page(s): 2215 - 2218
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    This paper develops a robust and fast parametric model to describe the dynamic behavior of an ac contactor. The model solves simultaneously the mechanical and electromagnetic coupled differential equations that govern its dynamic response. It deals with the shading rings and takes into account the fringing flux. Data from simulations carried out by applying the presented parametric model are compared with experimental data, demonstrating the model's validity and effectiveness. View full abstract»

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  • Efficient Modeling of Magnetostrictive Media Using Fuzzy Inference Systems

    Publication Year: 2008 , Page(s): 2219 - 2226
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (533 KB) |  | HTML iconHTML  

    Magnetic materials exhibiting giant magnetostriction, such as Terfenol, are currently widely used in fine positioning and active vibration damping devices. Obviously, using accurate magnetostriction simulation models during the various design stages of those devices can positively contribute to the enhancement of their precision. This paper presents an efficient approach, based on fuzzy inference systems, for modeling magnetostrictive media. More precisely, the proposed approach offers a computationally low-cost methodology to model interdependencies of strain and flux density on applied stress and magnetic field. The paper gives details of the modeling methodology and its experimental testing. View full abstract»

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  • Servo Control Design for a High TPI Servo Track Writer With Microactuators

    Publication Year: 2008 , Page(s): 2227 - 2234
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1304 KB) |  | HTML iconHTML  

    This paper proposes modifications to enhance the original generalized Kalman-Yakubovic-Popov (G-KYP) lemma-based sensitivity function shaping technique that Q-parameterizes the controller and solves for the desired finite impulse response filter Q(z) using linear matrix inequalities (LMI) optimization. By representing Q(z) with an infinite impulse response filter and including an extra LMI that is derived based on the bounded real lemma into the original LMI optimization algorithm, our modifications avoid such problems as unnecessary increase and decrease in sensitivity gain at various frequency ranges, large sensitivity peak, degradation in noise rejection, and insufficient stability robustness against plant uncertainty. In other words, the proposed scheme achieves a better compromise between disturbance and noise rejection performance and stability robustness. The proposed control design was applied to a servo track writing platform. Experimental results show that the control design based on our proposed scheme further reduces the true PES NRRO 3sigma from 6 nm to 5.7 nm and improves the closed-loop stability robustness by 5.1%. View full abstract»

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  • Low-Density Parity-Check Coded Recording Systems With Run-Length-Limited Constraints

    Publication Year: 2008 , Page(s): 2235 - 2242
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (291 KB) |  | HTML iconHTML  

    We propose two techniques for the low-density parity-check (LDPC) coded partial response channel with run-length-limited (RLL) constraints. The first is a modification of the selective flipping technique so that side information is not needed. The second is based on the estimation of flipped bits for the selective flipping technique. The second technique can achieve significant performance improvement over the simple selective flipping technique either with side information or without side information. We also incorporate these two techniques into a known technique to design LDPC coded recording systems that can meet strict RLL constraints without performance degradation. View full abstract»

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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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology