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Magnetics, IEEE Transactions on

Issue 2  Part 2 • Date March 1999

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  • IEEE Transactions on Magnetics 1999 Subject Categories

    Publication Year: 1999 , Page(s): 1091 - 1092
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  • New fabrication method for planar multilayer windings used in low-profile magnetic components

    Publication Year: 1999 , Page(s): 1055 - 1059
    Cited by:  Papers (5)  |  Patents (1)
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    A new design and fabrication method for planar windings with multilayers is presented. This method can virtually eliminate external soldering or conductive vias, thus reducing dc resistance and increasing reliability. Compared to the previously reported folding methods for winding fabrication, this method maximizes the use of the window height and minimizes the waste of copper area in manufacturing. The winding pattern is cut using a computer numerically controlled machine, or the punching/pressing process, which is cleaner than the commonly used etching process. The whole winding assembly is completed by a folding process. The primary and secondary windings in a transformer can be interleaved, resulting in low leakage inductance. Practical examples of low-profile transformers and inductors were constructed and tested in an active-clamped forward dc-dc converter with self-driven synchronous rectifiers. Experimental results are presented to show that such transformers/inductors are particularly useful for the design of low-profile and high power density converter modules View full abstract»

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  • New (e,h) formulation coupling a finite element method and a boundary integral method for the computation of the interaction of waves with a conducting domain

    Publication Year: 1999 , Page(s): 1014 - 1018
    Cited by:  Papers (1)
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    A variational formulation is presented to solve Maxwell's equations with the electric and magnetic fields as variables in waves interacting with a conducting domain. This method couples a finite element method and a boundary integral method. The discretization uses Nedelec's edge elements for both fields. We finally present numerical results View full abstract»

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  • New stable magnetodynamic suspension system

    Publication Year: 1999 , Page(s): 1047 - 1054
    Cited by:  Papers (6)
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    A new type of suspension is proposed here. This magnetodynamic suspension (MDS) system utilizes nonlinearities of magnetic permeability in steel cores to achieve a higher degree of stability for heavy moving bodies. The detailed structure of the proposed MDS system and its theoretical aspects are presented View full abstract»

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  • Evaluation of the anisotropy field for fine-particle systems from low-field thermomagnetic curves

    Publication Year: 1999 , Page(s): 1019 - 1023
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    A method for evaluating the temperature-dependent magnetic anisotropy field from thermomagnetic curves for Stoner-Wohlfarth-like systems is proposed. It allows the anisotropy parameters of a sample with unknown spontaneous magnetization to be obtained by using magnetic fields considerably lower than the anisotropy field View full abstract»

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  • Magnetic recording on FePt and FePtB intermetallic compound media

    Publication Year: 1999 , Page(s): 1077 - 1082
    Cited by:  Papers (17)  |  Patents (3)
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    Near-contact recording on high-coercivity FePt intermetallic compound media using a high Bsat write element was investigated. Untextured FePt media were prepared by magnetron sputtering on ZrO2 disks at a substrate temperature of 450°C, with postannealing at 450°C for 8 h. Both multilayer and cosputtered precursors produced the ordered tetragonal L10 phase with high coercivity between 5 and 12 kOe. To improve readback noise and decrease magnetic domain size, FePtB media were subsequently prepared by cosputtering. Overwrite, roll-off, signal-to-noise ratio (SNR), and nonlinear transition shift (NLTS) were measured by both metal-in-gap and merged magneto-resistive heads. FePtB media showed NLTS similar to that of commercial CoCrPtTa longitudinal media, but 5 dB lower SNR. By operating recording transducers in near contact, reasonable values of overwrite (>30 dB) could be obtained View full abstract»

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  • Pendulum experiments and the fundamental laws of electrodynamics

    Publication Year: 1999 , Page(s): 1060 - 1069
    Cited by:  Papers (1)
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    We utilize a more rigorous way to calculate the radiated electromagnetic energy and field momentum in electromagnetic impulse pendulum experiments previously carried out by various authors. We consider the impulse pendulum and the rest of the circuit as a magnetic dipole. Calculating the previous authors' wrongly defined vacuum reaction force Fvac we prove that this force is not equal to the Lorentz force FL as they stated. Specifically, we prove that Fvac arising from the whole loop is always equal to zero. We also prove that the field momentum Pfield arising from the whole loop is always equal to zero. In addition we show that the momentum imparted to the impulse pendulum is not equal to Pfield as they claim, and that the field energy radiated by the impulse pendulum is not equal to (mv)c, where mv is the momentum of the pendulum. Therefore, we have proven that the previous analysis is incorrect and not physically valid View full abstract»

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  • Optimal design of cylindrical air-gap synchronous permanent magnet couplings

    Publication Year: 1999 , Page(s): 1037 - 1046
    Cited by:  Papers (21)
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    Different types of structures for ironless synchronous cylindrical air-gap permanent magnet couplings are studied. In these structures, radially and tangentially oriented magnets are placed in ironless cores. The structures present a very small inertia and offer important benefits in many cases. An efficient method to calculate the torque of these types of couplings is presented. It is based on analytical formulas for the forces between parallelepipedical magnets. Optimal designs for each type of coupling and each number of pole pairs are determined by using a nonlinear optimization method. The design results are analyzed. The different types of structure are compared. The influence of the number of pairs of poles and of the main characteristic dimensions of each coupling is discussed. The results show that an ironless coupling structure where both radially and tangentially oriented magnets are used is a very advantageous solution View full abstract»

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  • Williams-Comstock model with finite-length transition functions

    Publication Year: 1999 , Page(s): 1070 - 1076
    Cited by:  Papers (3)  |  Patents (1)
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    The theory of the third-order-polynomial (TOP) and fifth-order-polynomial (FOP) magnetization transitions is presented. These transitions have a finite length, rather than an asymptotic approach to ±Mr., which is the case with some widely-used transition functions. The Williams-Comstock model is used to obtain the transition parameters, which are equal to half the transition lengths, resulting in quadratic equations and simple expressions. In this analysis, the write-field gradient is maximized with respect to the deep-gap field, as well as with respect to the distance of the transition from gap center, which results in a higher gradient than is obtained with the original Williams-Comstock approach, at the expense of a higher write current. Analytic expressions are obtained for the read pulses of inductive and shielded magnetoresistive heads, and equations for nonlinear transition shift are derived for the arctangent and the TOP transitions. The results are compared with those obtained using arctangent and tanh transitions and with experiment. In addition, certain aspects of the write-process Q function and the optimum deep-gap field are discussed View full abstract»

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  • Adaptation of an all-pass equalizer for decision feedback equalization

    Publication Year: 1999 , Page(s): 1083 - 1090
    Cited by:  Papers (4)
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    Recording channels using decision feedback equalization require a minimum phase response and white noise at the detector to achieve maximum signal-to-noise ratio. A low order all-pass filter can equalize the feedforward path so that it approximately achieves a minimum phase response. In this paper, we describe an adaptive algorithm for iteratively determining the optimal transfer function of the all-pass filter. Adaptation is based on estimating the gradient of the mean-square error with respect to the poles of the filter. This estimate is then used to update the positions of the poles. One simplifying feature of this technique is that these gradients are determined by applying the output of the all-pass to low-order finite impulse response (FIR) filters. We do not require values from the internal states of the filter. The proposed adaptation algorithm is characterized for first- and second-order all-pass filters over a range of storage densities. The optimality of the resulting equalizer is evaluated as a function of the order of the FLR filters used in estimating the gradients View full abstract»

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  • Microwave bistability in a magnetostatic wave interferometer with external feedback

    Publication Year: 1999 , Page(s): 1024 - 1036
    Cited by:  Papers (12)
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    Microwave bistability has been obtained for the first time in a magnetostatic wave (MSW) interferometer with external magnetic field feedback. The interferometer contained a magnetostatic surface wave transmission line with a 7.5-μm thick epitaxial film of yttrium iron garnet magnetized with an external static magnetic field of 1048 Oe, a variable attenuator in a parallel reference channel, and external feedback in the form of an additional static field derived from the line output. Bistable and multistable output power versus input power responses are derived from the frequency dependence of the interferometer transmission and the MSW wave number dependence on the static magnetic field. Typical bistable and multistable output versus input power hysteresis loops were obtained under constant frequency operation in the range 4.9 to 5.2 GHz, and for input powers from -30 to +10 dBm. The bistable response depends on the frequency of the microwave signal, the attenuation in the reference channel, and the gain of the feedback loop. An analysis based on linear MSW theory agreed with experiment. Applications of MSW microwave bistability include power limiter devices and basic microwave logic elements 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