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Magnetics, IEEE Transactions on

Issue 6 • Date June 2005

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  • [Front cover]

    Publication Year: 2005 , Page(s): c1
    Cited by:  Papers (1)
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2005 , Page(s): c2
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  • Table of contents

    Publication Year: 2005 , Page(s): 2041 - 2042
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  • Co-Fe metal/native-oxide multilayers: a new direction in soft magnetic thin film design I. Quasi-static properties and dynamic response

    Publication Year: 2005 , Page(s): 2043 - 2052
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1120 KB) |  | HTML iconHTML  

    The progression toward gigahertz data rates in magnetic recording has introduced considerable challenges to soft magnetic materials design. The difficulties lie in satisfying two sets of conflicting demands: 1) simultaneously achieving soft magnetic properties, high saturation magnetization, and a high resistivity, with the latter required to limit eddy-current losses and 2) balancing the inherent tradeoff between bandwidth and permeability imposed by the direct and inverse dependences, respectively, of these two parameters on the anisotropy field. This paper describes a new soft magnetic composite system that meets these requirements: a metal/native-oxide multilayer (MNOM) film consisting of nanogranular high-moment CoxFe100-x layers separated by ultrathin magnetic native oxide layers. The high-resistivity magnetic oxide layers isolate the metallic layers electrically, while coupling them magnetically and minimizing the decrease in volume-averaged saturation magnetization that exists in traditional metal/nonmagnetic oxide composites. In addition, the "exchange-averaged" soft magnetic properties of the MNOM composite include an ideal low-dispersion in-plane uniaxial anisotropy whose magnitude varies linearly with the fraction x of Co in the alloy. The resulting anisotropy control, together with the large saturation magnetization, permits the permeability and resonance frequency to be tuned over a wide range to meet specific application requirements. View full abstract»

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  • Co-Fe metal/native-oxide multilayers: a new direction in soft magnetic thin film design II. Microscopic characteristics and interactions

    Publication Year: 2005 , Page(s): 2053 - 2063
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB) |  | HTML iconHTML  

    CoxFe100-x metal/native-oxide multilayer (MNOM) films exhibit soft magnetic properties, large magnetization, high resistivity, and a potential operating bandwidth of several gigahertz. These attractive characteristics are facilitated by ultrathin magnetic native oxide layers introduced to provide a high-resistivity barrier between nanocrystalline metal layers while preserving interlayer coupling and contributing to the net moment. This paper addresses several important features of the MNOM system from a microscopic perspective. The uniaxial anisotropy of MNOM thin films is discussed in detail and "exchange averaging" is invoked to account for its vanishingly small effective dispersion. The role of the native oxide in establishing interlayer exchange coupling is demonstrated, and a detailed account of the nature of the oxide is presented. In the Fe MNOM system, the oxide is shown to have a volume-averaged magnetization of 732(35) emu/cm3, with a temperature dependence comparable to that of metallic Fe. The magnetism of this largely "interfacial" oxide is supported by the metal and collapses in the absence of the metal. The oxide retains a large net moment for Co fractions up to at least x=50, but oxide magnetism is lost at high Co fractions, coinciding with the loss of soft magnetic properties. View full abstract»

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  • Characterization and microwave absorbing properties of Nd-Fe-Ti intermetallic compounds derived from Nd-Fe-B sintered magnet scraps

    Publication Year: 2005 , Page(s): 2064 - 2070
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1184 KB) |  | HTML iconHTML  

    Nd-Fe-Ti intermetallic compounds were prepared from rare earth sintered magnet scrap powders (Nd2Fe14B sludge) and Ti by arc-melting and solidification processes. The resulting alloy ingots were ground into fine powders and some of them were heated at 100°C-250°C for 1-12 h in air. The epoxy resin composites with 83 wt% of these powders showed good microwave absorption properties at gigahertz range, and the maximum absorption peak of -39.4 dB was observed at 12.3 GHz after heating at 250°C for 3 h in air. Compared to Fe-Ti intermetallic compound powders prepared from fresh metals of Fe and Ti, the sludge-derived Nd-Fe-Ti powders showed higher oxidation resistivity due to the preferential oxidation of Nd content. View full abstract»

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  • Modeling of magnetostriction in particulate composite materials

    Publication Year: 2005 , Page(s): 2071 - 2076
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    By combining a magnetostrictive material with a polymer or a metal, the magnetostrictive composites can have a reasonably large magnetostriction response for various sensor and actuator applications. In this paper, a relatively simple model for studying the magnetostrictively induced deformation behavior of magnetostrictive composites is presented. For illustrative purposes, we calculate the magnetostriction responses of composites containing Terfenol-D and nickel. Through numerical calculation, we have obtained the macroscopic longitudinal strains parallel to the applied magnetic field for Terfenol-D/glass composite and both longitudinal and transverse strains for the nickel/epoxy composite. Comparison with experimental data for both material systems shows our model is applicable up to very high volume fraction of magnetostrictive inclusions. View full abstract»

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  • Demagnetizing factors for rectangular prisms

    Publication Year: 2005 , Page(s): 2077 - 2088
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1424 KB) |  | HTML iconHTML  

    For rectangular prisms of dimensions 2a×2b×2c with constant material susceptibility χ, we have calculated and tabulated the fluxmetric and magnetometric demagnetizing factors Nf and Nm, defined along the 2c dimension as functions of c/(ab)12/(=1∼500), a/b(=1∼256), and χ(=0∼109). We introduce an interpolation technique for obtaining Nf,m with arbitrary values of c/(ab)12/, a/b, and χ. View full abstract»

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  • Stability of an electromagnetically levitated spherical sample in a set of coaxial circular loops

    Publication Year: 2005 , Page(s): 2089 - 2101
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    This paper presents a theoretical study of oscillatory and rotational instabilities of a solid spherical body, levitated electromagnetically in axisymmetric coils made of coaxial circular loops. We apply our previous theory to analyze the static and dynamic stability of the sample depending on the ac frequency and the position of the sample in the coils for several simple configurations. We introduce an original analytical approach employing a gauge transformation for the vector potential. First, we calculate the spring constants that define the frequency of small-amplitude oscillations. For static stability, the spring constants must be positive. Dynamic instabilities are characterized by critical ac frequencies that, when exceeded, may result either in a spin-up or oscillations with increasing amplitude. We found that the critical frequencies increase with the nonuniformity of the field. We show that for a spherically harmonic field, the critical frequency for the spin-up instability in a field of degree l coincides with the critical frequency for the oscillatory instability in a field of degree l+1. View full abstract»

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  • Model-based characterization of homogeneous metal plates by four-point alternating current potential drop measurements

    Publication Year: 2005 , Page(s): 2102 - 2110
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    We determined the conductivity, relative permeability, and thickness of homogeneous metal plates from four-point measurements of alternating current potential drop (ACPD) over the frequency range 1 Hz to 10 kHz. We developed simple analytical expressions from which these parameters can be calculated. In the low-frequency regime, in which the measured voltage tends to a constant, real value, the relative permeability of the plate does not influence the ACPD voltage. For known plate thickness, conductivity can be easily determined, even for ferrous metals. For known conductivity, plate thickness can be determined. Relative permeability can be obtained from measurements at higher frequency, for known conductivity and thickness. The inductance of the pickup circuit can also be determined from higher frequency measurements. This practical technique is especially useful for conductivity or plate thickness measurements in configurations where access is restricted to one side of the plate. We studied brass, aluminum, stainless steel, spring steel, and carbon steel plates. Our results agree with available independent measurements. View full abstract»

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  • A response surface methodology based on improved compactly supported radial basis function and its application to rapid optimizations of electromagnetic devices

    Publication Year: 2005 , Page(s): 2111 - 2117
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB) |  | HTML iconHTML  

    The compactly supported radial basis function (CS-RBF) is improved and used to design a new response surface model. The model is incorporated into stochastic global optimal methods to develop a fast and efficient global optimal design strategy with the main target to reduce the number of function calls that involve computationally heavy procedures such as, for example, the repetitive usage of finite element analysis which is generally required in solving inverse problems. In order to employ a multistep method to automatically adjust the support of the CS-RBF to realize the "best" tradeoff between computational efficiency and accuracy, a cluster algorithm is proposed to decompose the sample points into a nested sequence of subsets. To validate the proposed algorithm, typical numerical results on two different examples are reported. View full abstract»

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  • Hysteresis model for finite-element analysis of permanent-magnet demagnetization in a large synchronous motor under a fault condition

    Publication Year: 2005 , Page(s): 2118 - 2123
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    This paper describes a rare-earth-transition metal alloy permanent-magnet (Nd2Fe14B) hysteretic behavior model within finite-element analysis. The present work analyzes the demagnetization states of permanent magnets during fault conditions in a permanent-magnet synchronous motor and characterizes the ability of the motor to sustain the designed rated outputs after the fault conditions occur. View full abstract»

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  • Thermal analysis of soft magnetic composite motors using a hybrid model with distributed heat sources

    Publication Year: 2005 , Page(s): 2124 - 2128
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    This paper presents a hybrid thermal model with distributed heat sources for thermal analysis of soft magnetic composite (SMC) motors. The model uses a combination of lumped and distributed thermal parameters, which can be obtained from motor dimensions and thermal constants. The model can be used to calculate the core loss in each part, in combination with three-dimensional magnetic field finite-element analysis. The thermal model is applied to calculate the temperature distributions in a claw pole permanent-magnet motor with SMC stator. View full abstract»

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  • Transient response in magnetocaloric regeneration

    Publication Year: 2005 , Page(s): 2129 - 2133
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    We report on the first experimental demonstration of the details of the transient response in the four sequential processes of active magnetic regenerative refrigeration: magnetization, warm blow, demagnetization, and cold blow. The experimental results display the details of the gradual temperature divergence due to regeneration. The temperature change of the stationary solid bed is due to the magnetocaloric effect in a periodic field. The theory for the active magnetic regenerative refrigeration is applied to the transient processes in magnetocaloric regeneration. A time and spatial dependent model of temperature profile of the magnetization and demagnetization with thermal wave regenerative processes is developed. View full abstract»

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  • A target-field method to design circular biplanar coils for asymmetric shim and gradient fields

    Publication Year: 2005 , Page(s): 2134 - 2144
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB) |  | HTML iconHTML  

    The paper presents a method for designing circular, shielded biplanar coils that can generate any desired field. A particular feature of these coils is that the target field may be located asymmetrically within the coil. A transverse component of the magnetic field produced by the coil is made to match a prescribed target field over the surfaces of two concentric spheres (the diameter of spherical volume) that define the target field location. The paper shows winding patterns and fields for several gradient and shim coils. It examines the effect that the finite coil size has on the winding patterns, using a Fourier-transform calculation for comparison. View full abstract»

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  • Development of analytical models of switched reluctance motor in two-phase excitation mode: extended Miller model

    Publication Year: 2005 , Page(s): 2145 - 2155
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB) |  | HTML iconHTML  

    This paper models the magnetic coupling effects of phase windings in a typical two-phase excited 6/4 switched reluctance motor (SRM). The flux-linkage characteristics, obtained from the two-dimensional finite-element analysis of the motor, show the major effect of the mutual coupling between the phases particularly for high levels of phase currents. Because the flux-linkage characteristic fully describes the motor behavior, the flux-linkage model is the base for this analysis. Taking into account the advantages of the Miller model, we extended it to two-phase excitation. Even though we used a simple, low-cost, and easily implemented model, it can reasonably predict the flux-linkage characteristics of the two-phase excited SRM. We compared the proposed method with the results of the method reported by Essah and Sudhoff and found that more accurate results are achieved with the proposed method. View full abstract»

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  • A novel synchronous permanent magnet planar motor and its model for control applications

    Publication Year: 2005 , Page(s): 2156 - 2163
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    A novel synchronous permanent magnet planar motor (SPMPM) with iron core is proposed. It has higher continuous force compared to the coreless SPMPM. In the novel SPMPM, two sets of windings for generating x-direction thrust and y-direction thrust are perpendicularly fixed in the x-direction slots and y-direction slots of a mover core, respectively. For control system development applications, an electromagnetic model is derived and the analytical method for calculating the model parameters is also reported. The model describes an important characteristic of the novel SPMPM that the x-direction thrust and y-direction thrust are independent of each other. To verify the model and the parameter calculation method, the finite element method (FEM) is used for calculating the phase inductances and electromagnetic forces of an example SPMPM. The results from FEM are in good agreement with the results from the analytical equations. It demonstrates the feasibility and credibility of the proposed model and parameter calculation method to a certain extent. View full abstract»

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  • Effects of magnetically induced vibration force in brushless permanent-magnet motors

    Publication Year: 2005 , Page(s): 2164 - 2172
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB) |  | HTML iconHTML  

    This paper discusses magnetic force imbalance and cogging torque in permanent-magnet motors under both static and dynamic rotor eccentricity. The characteristic frequencies of magnetic force imbalance and cogging torque due to rotor eccentricity can be used for fault diagnostics and quality control of permanent-magnet motors. The paper derives analytical expressions for their characteristic frequencies. The validity of the expressions has been confirmed by finite-element analyses. View full abstract»

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  • Magnetically induced vibration in a permanent-magnet brushless DC motor with symmetric pole-slot configuration

    Publication Year: 2005 , Page(s): 2173 - 2179
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB) |  | HTML iconHTML  

    The paper reports a numerical and experimental study of magnetically induced vibration associated with rotor/stator eccentricity and imperfect magnetization for 8-pole 6-slot symmetric brushless dc (BLDC) motors. Magnetic forces and cogging torque are calculated for various slot angles by using the finite-element method (FEM). The results show that there is an optimal slot angle for minimum cogging torque, but this slot angle is not optimal for reducing magnetic forces. In the idle acoustics test, the motors with reduced magnetic forces show clear reduction at the expected frequencies while the motors with minimum cogging torque show no change at the cogging torque frequency, which implies unbalanced magnetic forces have greater effect on actual vibration of the spindle motor than cogging torque. The results show that the proper direction in motor design is to reduce unbalanced magnetic forces when both cogging torque and unbalanced magnetic forces are not achievable simultaneously. View full abstract»

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  • Design, modeling, and seek control of a voice-coil motor actuator with nonlinear magnetic bias

    Publication Year: 2005 , Page(s): 2180 - 2188
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2176 KB) |  | HTML iconHTML  

    The research investigates the feasibility and trajectory tracking performance of an adaptive controller applied to a voice-coil motor actuator (VCMA) influenced by nonlinear magnetic bias. A magnetic bias feature on the actuator arm is designed to compensate for nonoperational shock. Because the resulting bias is nonlinear and uncertain, a model-based adaptive controller was developed to meet the seek performance requirements and simultaneously handle effects of the nonlinear bias. A VCMA with the bias feature was manufactured according to the design requirements. Extensive experiments were conducted to characterize the VCMA physical parameters and verify the controller performance. The effects of sample rate and bias modeling accuracy are also discussed. A representative sample of the results is presented. View full abstract»

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  • Cross-track transition location and transition parameter effects in heat-assisted magnetic recording

    Publication Year: 2005 , Page(s): 2189 - 2194
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    When conventional longitudinal and perpendicular magnetic recording architectures reach their well-known superparamagnetic limits, one candidate to break through the limit is heat-assisted magnetic recording (HAMR). In this paper, we investigate the effect of cross-track transition location and transition parameter (a-parameter) profiles in an HAMR system. Here, we apply microtrack modeling and the thermal Williams-Comstock model to longitudinal recording to determine the transition location and a-parameter profiles along the cross-track direction in the presence of a temperature profile. We then explore the effect of temperature on the isolated transition response of the system. View full abstract»

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  • Recording performance of discrete track patterned media fabricated by focused ion beam

    Publication Year: 2005 , Page(s): 2195 - 2198
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB) |  | HTML iconHTML  

    We report on the recording performance of discrete track patterned media fabricated by focused ion beam (FIB). We investigated performance over a small area by spinstand read/write testing. Discrete track patterned regions show smaller magnetic track width and better signal separation between adjacent tracks and therefore higher track density than that of nonpatterned continuous media as a result of reduced side fringe effect and edge noise. We found that, at a designed groove depth of 4-8 nm, the shallow FIB etched grooves already provide good isolation between adjacent tracks, indicating the superiority of ion beam induced modification of magnetic properties in film media over physical modification of disk surface topography. This has implications for discrete track recording and media fabrication. View full abstract»

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  • Novel bidirectional linear actuator for electrohydraulic valves

    Publication Year: 2005 , Page(s): 2199 - 2201
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    This paper presents a permanent-magnet actuator with bidirectional and high levels of linear force over short strokes. The actuator can be used in electrohydraulic valves. Its static and dynamic performances were analyzed by using two-dimensional finite-element magnetic field solutions that take into account the nonlinearity of the material. The measured and simulated results are highly consistent. Experimental results show that the prototype actuator can produce a force of ±60 N, its nonlinearity is less than 0.5%, and the hysteresis is less than 2% within a stroke of ±1 mm. The actuator's frequency response (-3 dB) can reach 150 Hz. View full abstract»

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  • Cogging force reduction of two-phase linear hybrid stepping motor

    Publication Year: 2005 , Page(s): 2202 - 2204
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    This paper presents a π/4-multiple-coupled two-phase linear hybrid stepping motor (LHSM) that has two windings per phase, one of which shares the other phase winding. The proposed motor shows a unique ability to deliver low cogging force without any complex control scheme or additional power electronics hardware in microstepping control. An analytical and experimental comparison between conventional π/2- and π/4-multiple-coupled LHSM confirms the effectiveness of the proposed design. View full abstract»

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  • IEEE Magnetics Society Information

    Publication Year: 2005 , Page(s): c3
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    Freely Available from IEEE

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