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Magnetics, IEEE Transactions on

Issue 7  Part 1 • Date July 2008

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  • [Front cover]

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

    Page(s): C2
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  • Table of contents

    Page(s): 1685 - 1686
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  • Advances in Giant Magnetoresistance Biosensors With Magnetic Nanoparticle Tags: Review and Outlook

    Page(s): 1687 - 1702
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2187 KB) |  | HTML iconHTML  

    We present a review of giant magnetoresistance (GMR) spin valve sensors designed for detection of magnetic nanoparticles as biomolecular labels (nanotags) in magneto-nano biodetection technology. We discuss the intricacy of magneto-nano biosensor design and show that as few as approximately 14 monodisperse 16-nm superparamagnetic nanoparticles can be detected by submicron spin valve sensors at room temperature without resorting to lock-in (narrow band) detection. GMR biosensors and biochips have been successfully applied to the detection of biological events in the form of both protein and DNA assays with great speed, sensitivity, selectivity, and economy. The limit of molecular detection is well below 10 pM in concentration, and the protein or DNA assay time can be under two hours. The technology is highly scalable to deep multiplex detection of biomarkers in a complex disease, and amenable to integration of microfluidics and CMOS electronics for portable applications. On-chip CMOS circuitry makes a sensor density of 0.1-1 million sensors per square centimeter feasible and affordable. The theoretical and experimental results thus far suggest that magneto-nano biochip-based GMR sensor arrays and nanotags hold great promise in biomedicine, particularly for point-of-care molecular diagnostics of cancer, infectious diseases, radiation injury, cardiac diseases, and other diseases. View full abstract»

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  • Characterization of Mn–Zn Ferrites Using the Coaxial Transmission Line Method

    Page(s): 1703 - 1710
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    In the coaxial transmission line method, a factor that greatly influences the accuracy of the results is the air gaps between the material under test and the coaxial transmission line test fixture. In this paper, we discuss the influence of the air gaps and the measures that can be taken to minimize that influence when Mn-Zn ferrites are measured. We propose an improved simulation model of the coaxial transmission line test fixture holding the material under test in which the air gaps are filled with conductive materials. By combining the improved simulation model, the mode-matching method, and the Newton-Raphson method, the Mn-Zn ferrites' intrinsic complex permeability and permittivity can be determined accurately, even if the conductor-filled gaps are quite wide. We also examine the influence of the finite conductivity of the coaxial transmission line test fixture. We manufactured a coaxial transmission line test fixture to measure the intrinsic complex permeability and permittivity of Mn-Zn ferrites in the frequency range from 10 to 200 MHz. The intrinsic values thus determined have been experimentally verified. We describe the structure of the test fixture, its calibration issues, and the experimental results. View full abstract»

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  • State-Space Constitutive Model for Magnetization and Magnetostriction of Galfenol Alloys

    Page(s): 1711 - 1720
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    We present a thermodynamic model that quantifies the magnetization and magnetostriction of annealed or unannealed Galfenol alloys subjected to magnetic fields and mechanical stresses. The model requires a small number of parameters directly related to physical properties of the data, thus providing a useful tool for material characterization and design. Furthermore, the model is formulated in state-space form, which simplifies computations for design and control of Galfenol devices. View full abstract»

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  • Improved Jiles–Atherton Model for Least Square Identification Using Sensitivity Function Normalization

    Page(s): 1721 - 1727
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (478 KB) |  | HTML iconHTML  

    We present an improved version of the Jiles-Atherton model for least square identification. We first use a simplified anhysteretic magnetization model to provide simple estimates of the initial parameters. Then we perform a normalization of sensitivity functions to improve the convergence of the Levenberg-Marquardt algorithm, leading to the emergence of optimal parameters. Experimental trials validate our method. View full abstract»

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  • A Field-Extrema Hysteresis Loss Model for High-Frequency Ferrimagnetic Materials

    Page(s): 1728 - 1736
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    We present a new field-extrema hysteresis loss model (FHM) for high-frequency ferrimagnetic materials, along with a parameter identification procedure. The model does not involve solving an ordinary differential equation (ODE) and is asymmetric in that it works well under dc bias conditions. In the proposed model, the loss calculations are based on the extrema values of the fields. The model includes the effects of magnetic saturation as well as frequency effects. The model is comparable in accuracy to the ODE-based Jiles-Atherton model, but retains the convenience and computational efficiency of an empirical model. We demonstrate a procedure to characterize the model parameters using the Jiles-Atherton model. We compare magnetic hysteresis loss calculated by our new model with a full time-domain solution, as well as an empirical model, for a sample high-frequency ferrite. We demonstrate the use of the model, and validate the model, by calculating magnetic loss in an EI core inductor operating as the filter inductor in a buck converter. The model and identification procedure are being endorsed as a useful framework for computing magnetic loss in the context of automated magnetic device design. View full abstract»

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  • Optimal Design of an Electromagnetic Coupler to Maximize Force to a Specific Direction

    Page(s): 1737 - 1742
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (894 KB) |  | HTML iconHTML  

    This study suggests a concept design for an electromagnetic (EM) coupler, using the topology optimization method. To maximize the force generated by magnetic flux, the magnetic energy generated must be differentiable, at the location where the force is acting, in a prescribed force direction. This study proposes a topology optimization scheme for maximizing the force in a specific direction, using a commercial analysis program, ANSYS, to provide the force value. We use ANSYS for obtaining the resultant force as well as analyzing the magnetic field. We adopt a density calculation method called SIMP (solid isotropic material with penalization), and compute the sensitivity of the objective function according to the density change of each finite element in the design domain. As a result, optimal shapes of the core and the armature of the coupler are obtained and the performance is verified. View full abstract»

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  • Calculating Mutual Inductance Between Circular Coils With Inclined Axes in Air

    Page(s): 1743 - 1750
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    In this paper we present a lucid, easy, and accurate approach for calculation of the mutual inductance between all inclined circular coils with either rectangular cross section or negligible section. We use Grover's formula for the mutual inductance between two filamentary circular coils with inclined axes that lie in the same plane. Their centers are either displaced along the axis of one coil or displaced along one axis of the first coil and then displaced sideways in addition. We apply the filament method for coil combinations comprising circular coils of rectangular cross section, thin wall solenoids, thin disk coils (pancakes), and filamentary circular coils. In this approach we clarify how Grover's formulas have to be used for different coil combinations in the filament treatment. Thus, two well-known methods (Grover's formulas and the filament method) can be easily used to calculate the mutual inductance between all inclined circular coils, even though the problem is purely three-dimensional. View full abstract»

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  • Analytical and Numerical Techniques for Solving Laplace and Poisson Equations in a Tubular Permanent-Magnet Actuator: Part I. Semi-Analytical Framework

    Page(s): 1751 - 1760
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1372 KB) |  | HTML iconHTML  

    We present analytical and numerical methods for determining the magnetic field distribution in a tubular permanent-magnet actuator (TPMA). In Part I, we present the semianalytical method. This method has the advantage of a relatively short computation time and it gives physical insight. We make an extension for skewed topologies, which offer the benefit of reducing the large force ripples of the TPMA. However, a lot of assumptions and simplifications with respect to the slotted structure have to be made in order to come to a relatively simple semianalytical description. To model the slotting effect and the related cogging force, we apply a Schwarz-Christoffel (SC) mapping for magnetic field and force calculations in Part II of the paper. Validation of the models is done with finite-element analysis. View full abstract»

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  • Analytical and Numerical Techniques for Solving Laplace and Poisson Equations in a Tubular Permanent Magnet Actuator: Part II. Schwarz–Christoffel Mapping

    Page(s): 1761 - 1767
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (786 KB) |  | HTML iconHTML  

    In Part I of the paper, we derive a semianalytical framework for the magnetic field calculation in the air gap of a tubular permanent-magnet (PM) actuator. We also make an extension for skewed topologies. However, the slotting effect and its related cogging force cannot be determined in a straightforward way. Therefore, in Part II, we apply the Schwarz-Christoffel (SC) conformal mapping method to one pole-pair of the tubular PM actuator. This mapping allows for field calculation in a domain where standard field solutions can be used. In this way, slotting effects can be taken into account; however, skewing cannot be implemented directly. The SC-conformal mapping method is valid only for two-dimensional Cartesian domains. We therefore apply a special transformation from the cylindrical to the Cartesian coordinate system to describe the tubular actuator as a linear actuator. View full abstract»

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  • Nano Ferrites Microwave Complex Permeability and Permittivity Measurements by T/R Technique in Waveguide

    Page(s): 1768 - 1772
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    There is a huge demand to accurately determine the magnetoelectrical properties of particles in the nano-sized regime due to the modern IC technology revolution and biomedical applications. In this paper, we present a microwave waveguide measurement technique for measuring complex permeability and permittivity of expensive nano-sized magnetic powder materials. We used a vector network analyzer to provide a standard TRL calibration for free space inside waveguide measurements. In order to maintain the recommended insertion phase range, a very thin prepared sample was loaded inside the calibrated waveguide. The loaded material's magnetic and dielectric effects were also considered in the cutoff wavelength calculation of the propagation constant of the TE10 wave from the geometrical dimensions of the waveguides. These provisions make the permeability and permittivity measurements more reliable than those found by commonly used techniques. We used six different compounds of nano-sized ferrite powders (Fe3O4, CuFe2O4, CuFe2O4Zn, F12NiO3Zn, BaFe12O19, and SrFe12O19), in which the average diameter of nano particles is less than 40 nm, for measurement purposes. We measured the complex permeability and permittivity from 3.95 to 5.85 GHz. The results show that the dielectric permittivity of these materials is quite different from that of solid-state materials. View full abstract»

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  • Partial Demagnetization of Permanent Magnets in Electrical Machines Caused by an Inclined Field

    Page(s): 1773 - 1778
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (690 KB) |  | HTML iconHTML  

    We report a study of partial demagnetization of axially pressed sintered Nd-Fe-B magnets by inclined pulse demagnetization measurements, including a recoil behavior of the Nd-Fe-B material. From these measurements, we develop a simple empirical model for demagnetization of Nd-Fe-B magnets caused by an inclined field. We calculate demagnetization of a simple surface-magnet machine and a two-pole high-speed machine by using an exponent function-based model, taking also the inclined demagnetizing field into account. We show that it is not enough to consider only antiparallel demagnetizing field components in accurate demagnetization calculations. View full abstract»

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  • Quantitative Current Evaluation Through Magnetic Field Detection by Magnetic Force Microscopy

    Page(s): 1779 - 1784
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    We observed magnetic fields induced by a current passing through a fine path by magnetic force microscopy (MFM) in order to investigate the possibility of evaluating the current with high spatial resolution. In particular, we examined the magnetic field around an artificial current network to provide quantitative data on the method when a torsional displacement was imposed on an MFM cantilever by the magnetic force. Although the torsional displacement signal included some background offset, data calibration could be performed by subtracting the background from the original torsional signal, and the data after calibration was compared with the current value expected from the network structure. The calibrated data showed relatively good consistency with the expected value, which indicates the suitability of MFM observation of the magnetic field in quantitative evaluation of current. View full abstract»

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  • A New Cogging-Free Permanent-Magnet Linear Motor

    Page(s): 1785 - 1790
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    The cogging force of a permanent-magnet linear motor (PMLM) is a major component of the detent force, but unfortunately makes a ripple in the thrust force and induces undesired vibration and acoustic noise. It also deteriorates the control characteristics, particularly in regard to precise speed and position control. In this paper, we propose a new PMLM having a 9-pole 10-slot structure in order to reduce the cogging force. Our PMLM is properly wound for three-phase driving. Through a theoretical and finite-element analysis, we show that the 9-pole 10-slot PMLM removes almost all of the cogging force while giving 10% and 23% larger back-electromotive force and thrust force, respectively, than a conventional 8-pole 12-slot PMLM under the same conditions of exciting current, total number of windings, and total PM volume. View full abstract»

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  • Investigation of End Effects in Linear Induction Motors by Using the Finite-Element Method

    Page(s): 1791 - 1795
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (449 KB) |  | HTML iconHTML  

    In rotating machines, no end effects occur because of their cylindrical geometry, which has no ends in the direction of movement. In linear motors, however, either the rotor or the stator has a finite length, and end effects occur because of the part having finite length entering or exiting the magnetic field. End effects occur as magnetic waves having attenuation, and play a major role in the performance of linear induction motors (LIMs), especially at high speeds. As the speed increases, efficiency decreases because of longitudinal end effects. This decrease in efficiency has a braking effect. In high-speed maglev devices, such as trains, the efficiency and performance of the LIMs become very important. We report on our investigation of end effects by the finite-element method. View full abstract»

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  • Modeling of a 6/4 Switched Reluctance Motor Using Adaptive Neural Fuzzy Inference System

    Page(s): 1796 - 1804
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    The magnetic saturation and strong nonlinearity of switched reluctance machines (SRMs) makes it very difficult to derive a comprehensive mathematical model for the behavior of the machine. We propose a new method of modeling SRMs based on an adaptive neural fuzzy inference system (ANFIS). First, we use an indirect method to measure the static flux linkage and then use the co-energy method (via the principle of virtual displacement) to calculate the torque characteristics from data on flux linkage versus current and rotor position. A hybrid learning algorithm, which combines the back propagation algorithm and the linear least-squares estimation algorithm, identifies the parameters of the ANFIS. After training, the ANFIS flux linkage model and ANFIS torque model are in excellent agreement with experimental flux linkage measurements and the calculated torque data. Finally, we use an ANFIS current model and an ANFIS torque model to study SRM dynamic performance. The accuracy of the model was evaluated by comparison to laboratory measurements of the machine's current-speed and torque-speed characteristics. The model is quite accurate. View full abstract»

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  • Nonlinear Bearing Force and Torque Model for a Toothless Self-Bearing Servomotor

    Page(s): 1805 - 1814
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    We report developments in the modeling of bearing force and torque for a toothless self-bearing servomotor (TSBS), a permanent-magnet synchronous machine that utilizes the Lorentz force for levitation and torque simultaneously. The contactless nature and toothless construction of the device results in smooth torque production, making the TSBS ideal for precision pointing and slewing applications. We present, for the first time, nonlinear analytical expressions for force and torque based on first principle modeling. The parameters are identified from system data using linear least squares. The resulting nonlinear model aligns very well with finite-element analysis predictions. This approach has advantages over previous modeling efforts, which were purely analytical and always yielded linearized force and torque expressions. View full abstract»

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  • Optimized Winding Layout for Minimized Proximity Losses in Coils With Rod Cores

    Page(s): 1815 - 1821
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    In many cases, the proximity effect is the dominating loss mechanism in coils with rod cores at high frequencies. Therefore, overall power losses are influenced significantly by the winding layout of the coil. In this paper, we calculate the winding losses of inductors with rod cores, taking into account the two-dimensional field distribution at the wire positions as well as the magnetic fields caused by the eddy currents in adjacent windings. We show that the losses can be reduced by avoiding winding positions close to the ends of the ferrite core. We verify the results by measurements. View full abstract»

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  • Model-Order Reduction of Moving Nonlinear Electromagnetic Devices

    Page(s): 1822 - 1829
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (447 KB) |  | HTML iconHTML  

    We present a new approach for generating fast simulation models of electromagnetic (EM) devices that contain moving components and magnetic materials with nonlinear properties. Our approach is based on generating low-dimensional simulation models that approximate the original spatially discretized models of electromagnetic field and their variations under conditions of component movement and material nonlinearity. The movement of the modeled device components is simulated by coupling the reduced-order EM field models weakly to the mechanical equations. We have successfully used our approach to generate a fast simulation model of a simple electromagnetic device with a moving component and nonlinear material properties. View full abstract»

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  • Design and Analysis of a Maglev Planar Transportation Vehicle

    Page(s): 1830 - 1836
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    We describe the driving mechanism of a maglev planar transportation vehicle (MPTV). The levitation mechanism consists of four magnetic wheels and four rotary machines. The combination of the linear induction motor mechanisms enables the vehicle to travel with planar motion. The wheels provide stability without disturbing the planar motion. Because all the mechanisms use electrodynamic forces, the working range of the MPTV can be expanded simply by paving the workspace with a conductor. The feasibility of the MPTV has been verified in several experiments. View full abstract»

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  • Characterization of the Velocity Skin Effect in the Surface Layer of a Railgun Sliding Contact

    Page(s): 1837 - 1844
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    We present a characterization of contact velocity skin effect (VSEC), which is a major velocity- and efficiency-limiting effect at a railgun's sliding contact. Despite enormous contact forces, the armature remains separated from the rail by a thin layer, 4 to 12 A thick. Evidence suggests VSEC is also the primary mechanism responsible for the contact voltage drop. VSEC effects are seen in both electromagnetic launcher (EML) efficiency and breech voltage. We compare theoretical predictions of system efficiency and breech voltage to experimental measurements for both a conventional and an augmented railgun. The characterization of VSEC extends our previous theoretical work in this area and provides new insights into the physics of EML operation, especially with regards to the armature and sliding contact. VSEC is a significant energy loss mechanism and heat source, possibly contributing to contact erosion and transition. We propose a similar VSEC mechanism to explain velocity saturation and efficiency roll-off in plasma and hybrid armature railguns, as well as arc restrike. View full abstract»

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  • A Recursive Bayesian Estimation Method for Solving Electromagnetic Nondestructive Evaluation Inverse Problems

    Page(s): 1845 - 1855
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    Estimating flaw profiles from measurements is a typical inverse problem in electromagnetic nondestructive evaluation (NDE). This paper proposes a novel state-space approach for solving such inverse problems. The approach is robust in the presence of measurement noise. It formulates the inverse problem as a tracking problem with state and measurement equations. The state-space model resembles the classical discrete-time tracking problem. The model allows recursive Bayesian nonlinear filters based on sequential Monte Carlo methods to be applied in conjunction with numerical models that represent the measurement process (i.e., solution of the forward problem). We apply our approach to simulated eddy-current and magnetic flux leakage NDE measurements (with and without measurement noise) from known flaw shapes, and the results indicate the feasibility and robustness of the proposed method. View full abstract»

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  • Amplitude and Phase Distributions of Magnetization in Tunneling Magnetoresistive Heads

    Page(s): 1856 - 1860
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    We describe a thermal magnetic noise simulation of tunneling magnetoresistive (TMR) heads. We calculate the phase and amplitude distributions of the local noise resistance derived from the magnetization fluctuation of the free layer in the several gigahertz range and consider their relations with the magnetic noise spectrum. The results show that the phase distribution of the noise resistance strongly influences the second or higher resonant peaks in the magnetic noise spectrum of TMR heads. As an example, we show that the second resonant peak appears in the spectrum when the asymmetric magnetic field is applied to the free layer. 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.

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Meet Our Editors

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