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Magnetics, IEEE Transactions on

Issue 11 • Date Nov. 2005

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  • [Front cover]

    Publication Year: 2005 , Page(s): c1
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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): 4217 - 4218
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  • Mechanisms for electric and magnetic fields effects on biological cells

    Publication Year: 2005 , Page(s): 4219 - 4224
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    The application of electric and magnetic fields to biological systems can lead to changes that occur through a variety of physical mechanisms. These include changes in the ionic and molecular currents, changes in temperature due to heating, the lifetimes of free radicals, and the orientation of molecules. The importance of these mechanisms is a function of the biological system, the applied frequency, amplitude, and the length of exposure. These physical mechanisms, in turn, lead to changes in chemical reaction rates, molecular bindings to membranes, signaling between cells, and changes in the biology by way of changes in growth rates and cell functions, etc. In this paper, some ways in which measurements can be made to help sort out the physics leading to some of observed biological changes are described. View full abstract»

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  • Effects of calcining and sintering parameters on the magnetic properties of high-permeability MnZn ferrites

    Publication Year: 2005 , Page(s): 4225 - 4228
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    For asymmetric digital subscriber line (ADSL) technology applications, new MnZn ferrites are required with not only high initial permeability, but also with low hysteresis material constant ηB. The effects of calcining and sintering temperatures and oxygen equilibrium partial pressure on the magnetic properties of MnZn ferrites are studied in this work. It was found that raising the calcining temperature required a rise in the sintering temperature to simultaneously achieve maximum permeability and the lowest ηB value. Both grain size and porosity had an effect on the initial permeability of the samples. Porosity had an even larger effect on the ηB value than the initial permeability. Oxygen equilibrium partial pressure also had an important effect on the initial permeability and ηB value. In our testing range, both the initial permeability and the ηB value decreased with increasing value of A (oxygen parameter). In order to optimize synthesis conditions for the high initial permeability and low ηB value, it was best to calcine the sample at 950°C and sinter it at 1370°C, with A=7.55. View full abstract»

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  • Pure magnetooptic diffraction and Kerr microscopy of periodic domain structures

    Publication Year: 2005 , Page(s): 4229 - 4235
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1480 KB) |  | HTML iconHTML  

    The fabrication of a periodic domain structure in a ferromagnetic thin film is reported. This periodic domain structure is formed in a thin continuous magnetic film by coupling it to a periodic array of magnetic elements grown on top. When the array and the continuous film are exchange decoupled, magnetostatic interactions produce in the continuous layer a domain structure replica of the topographic pattern at selected field values. The present work reports a direct confirmation of this periodic domain structure in the flat continuous film by Kerr microscopy, which is responsible for the pure magnetooptic diffraction. The effect on the magnetization processes of oneand two-dimensional structures with different periodicities and dimensions is studied in detail and compared with micromagnetic simulations, for Co and Fe films. View full abstract»

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  • Micromagnetic study of the switching fields in polycrystalline magnetic thin-film media

    Publication Year: 2005 , Page(s): 4236 - 4241
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    In this paper, we use micromagnetic simulation to study the switching field reduction and the switching field distribution in polycrystalline thin-film media. We first show that, for the coupled magnetic particles, the switching field of the high-anisotropy particle is reduced as a result of the exchange coupling with the low-anisotropy particle. The switching field reduction increases almost linearly with the anisotropy difference between the coupled particles. An optimal exchange exists that gives a maximum switching field reduction. This switching field reduction is more severe for a small applied field angle; therefore, the angular sensitivity of the switching field is reduced compared to the Stoner-Wohlfarth relation. Detailed micromagnetic simulations also show that in polycrystalline thin-film media, because of the variation and the reduction of the magnetic properties at the grain boundaries, the media coercivity can be reduced significantly. The primary reason for this switching field reduction is the exchange interaction between the grain boundary and the grain center region. View full abstract»

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  • Use of novel adaptive digital feedback for magnetic measurements under controlled magnetizing conditions

    Publication Year: 2005 , Page(s): 4242 - 4249
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB) |  | HTML iconHTML  

    There are increasing calls to employ conventional magnetic testers, such as the Epstein frame and single sheet tester, for the accurate measurements of magnetic properties of soft magnetic materials under fully controlled nonsinusoidal flux density waveforms. This paper presents a computerized automated adaptive digital feedback system built for that purpose. We present several examples of the ability of the system to control an arbitrary shape of the flux density waveforms over the frequency range of the data acquisition system (0.5 Hz to 2 kHz) and for peak flux density up to 90% of saturation. The control algorithm is capable of magnetizing magnetic material under controlled sinusoidal, triangular, trapezoidal, and pulsewidth-modulated magnetizing conditions as well as other arbitrary waveforms that do not contain dc components. We provide a full description of the adaptive digital feedback technique together with measurements showing the B-H loops for several magnetic materials under various controlled excitation conditions. View full abstract»

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  • Coupled finite-element/boundary-element analysis of a reciprocating self-excited induction Generator in a harmonic domain

    Publication Year: 2005 , Page(s): 4250 - 4256
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    This paper suggests a general method for analysis of a reciprocating self-excited induction generator based on the coupled finite-element/boundary-element method in a harmonic domain. The finite-element method is used for iron and copper parts in order to deal with nonlinearity and eddy currents, while the boundary-element method is utilized for the air-gap region between the moving parts using a free-space Green function that facilitates the application of a linear time periodic movement. The proposed method leads to a static global matrix that is symmetrical for particular boundary conditions. The results agree well with those obtained by the time-stepping methods. View full abstract»

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  • Experimental development of a one-degree-of-freedom controlled magnetic linear bearing

    Publication Year: 2005 , Page(s): 4257 - 4260
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    We describe the architecture of a magnetic linear bearing with active control in only one direction, namely, the transverse direction of a moving table. The motions in the remaining directions, except the transverse direction, are restricted only by the action of permanent magnets. A control system composed of two electromagnets, a gap sensor, and a controller, keeps the table in a fixed transverse position. We explain the principle, the dynamic model for controlled direction, and the control system for the bearing. Finally, we describe experiments conducted on a prototype that show the effectiveness of the bearing architecture. View full abstract»

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  • Application of geometric programming to transformer design

    Publication Year: 2005 , Page(s): 4261 - 4269
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    This paper considers the transformer design optimization problem. In its most general form, the design problem requires minimizing the total mass (or cost) of the core and wire material while ensuring the satisfaction of the transformer ratings and a number of design constraints. The constraints include appropriate limits on efficiency, voltage regulation, temperature rise, no-load current, and winding fill factor. The design optimization seeks a constrained minimum mass (or cost) solution by optimally setting the transformer geometry parameters and the relevant electrical and magnetic quantities. In cases where the core dimensions are fixed, the optimization problem calls for a constrained maximum volt-ampere or minimum loss solution. This paper shows that the above design problems can be formulated in geometric programming (GP) format. The importance of the GP format stems from two main features. First, GP provides an efficient and reliable solution for the design optimization problem with several variables. Second, it guarantees that the obtained solution is the global optimum. The paper includes a demonstration of the application of the GP technique to transformer design. It also includes a comparative study to emphasize the advantage of including the transformer core dimensions as variables in the design problem. View full abstract»

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  • A simple unified physical model for a reluctance accelerator

    Publication Year: 2005 , Page(s): 4270 - 4276
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    In this paper, we develop an illustrative, physically unified model for treating a solenoidal reluctance linear accelerator. A simplified field-based physical model is developed from basic principles and cast in a variational (Lagrangian) form. The equations of motion are presented in a convenient form for computation, from which a fast and compact numerical model is constructed that also accounts for the effects of core saturation as well as the energy exchange between the field and armature motion. The results of this model are then compared with experimental results obtained from a small-scale mass launcher apparatus. Good agreement between experimental and computed behavior has been observed. View full abstract»

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  • Analysis of electromagnetic performance of flux-switching permanent-magnet Machines by nonlinear adaptive lumped parameter magnetic circuit model

    Publication Year: 2005 , Page(s): 4277 - 4287
    Cited by:  Papers (224)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1280 KB) |  | HTML iconHTML  

    A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed. View full abstract»

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  • Prediction and measurement of core losses in a high-speed switched-reluctance Machine

    Publication Year: 2005 , Page(s): 4288 - 4298
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1360 KB) |  | HTML iconHTML  

    We describe a procedure for calculating the core loss in high-speed switched-reluctance machines. The technique calculates core losses within a switched-reluctance machine to a high degree of spatial resolution over a wide range of operating conditions. We confirmed the calculations experimentally, using a loss segregation method, and found good correlation. View full abstract»

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  • High-efficiency, medium-caliber helical coil electromagnetic launcher

    Publication Year: 2005 , Page(s): 4299 - 4303
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1496 KB) |  | HTML iconHTML  

    Research progress in the development of a 40 mm×750 mm helical-coil electromagnetic launcher (HCEL) is presented and discussed. Significant technical problems that have been solved in this research include efficient stator commutation methods and the ability to simultaneously implement high-inductance gradient armatures. The HCEL is able to launch a 525-gram projectile to a velocity of 140 m/s. Power for the HCEL is derived from a 62.5 kJ sequentially fired pulse forming network (PFN) of 900 V (maximum) electrolytic capacitors. The experimentally measured HCEL efficiency of 18.2% is substantially greater than a conventional or augmented railgun of similar scale (i.e., equivalent mass, bore-size, and velocity). The HCEL's high launch efficiencies result from its 150 μH/m inductance gradient, which is approximately 300 times greater than the inductance gradient of a conventional railgun. HCEL computer model predictions are given and compared to experimentally measured HCEL and PFN parameters including peak current, inductance gradient, acceleration time, parasitic mass ratios, and electrical-to-kinetic conversion efficiency. Scaling relationships for the HCEL are also presented and used to predict launcher operation at higher velocity and with a larger diameter bore size. View full abstract»

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  • Evaluation of experimental permanent-magnet brushless motor utilizing new magnetic material for stator core teeth

    Publication Year: 2005 , Page(s): 4304 - 4308
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    We prepared motors with experimental cores using a soft magnetic composite and an amorphous metal and evaluated their performance. We measured the magnetic and motor characteristics, such as iron loss, when the new materials were used in the stator core teeth. The amorphous metal was found to have very high permeability and low iron loss, whereas the soft magnetic composite had low permeability and had a comparable iron loss as low-grade magnetic steel. The soft magnetic composite had the added benefits of being able to form a three-dimensional shape and having relatively low core loss in high frequency conditions. The magnetic properties we measured were able to predict the motor characteristics with high accuracy based on numerical and finite-element-method analysis. View full abstract»

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  • U-type piezoelectric thin-film microactuator for hard disk drives

    Publication Year: 2005 , Page(s): 4309 - 4314
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB) |  | HTML iconHTML  

    We have designed, fabricated, and investigated a new dual-stage actuator system based on a thin-film lead-zirconate-titanate (PZT) microactuator and a voice coil motor for positioning a magnetic head in a high-density hard disk drive (HDD). We made the PZT microactuator by using a modified sol-gel technique to deposit PZT thin film and applying reactive ion etching processes to shape the device. We studied the crystalline structure and growth behavior of the piezoelectric films by X-ray diffraction and scanning electron microscopy and found that the PZT material preferably has a composition of Pb(Zr0.52Ti0.48)O3. We also tested and simulated the U-type SUS304 substrate integrated with two single-layer PZT elements in order to investigate the driving mechanics. The device performance is outstanding. With the peak-to-peak head displacement of 1.08 μm at the applied voltage of ±20 V and the suspension response frequency higher than 12 kHz, both displacement/voltage sensitivity and resonant frequency are high enough for the device to be used in future high-density HDDs. View full abstract»

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  • PC-based position error signal generation and servo system for a spinstand

    Publication Year: 2005 , Page(s): 4315 - 4322
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB) |  | HTML iconHTML  

    We describe a high-performance servo control system for enhancement of spinstand servo performance. This PC-based system uses a multifunction I/O card for controller output and a high-speed digitizer card capable of sampling the frequency-encoded servo pattern at 500 MS/s. The PC, running under the Linux operating system, uses the Goertzel algorithm decoding scheme to calculate the position error signal (PES) at a 15-kHz update rate for feedback control. The control signal drives a custom-made lead zirconate titanate (PZT) actuator, which moves the suspension and thus the read/write head. A proportional and integral (PI) type servo controller supports a 1.1-kHz servo bandwidth, producing a 21.9% improvement of the positioning accuracy of the spinstand. View full abstract»

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  • Guaranteed scrambling

    Publication Year: 2005 , Page(s): 4323 - 4326
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    The bit-error rate (BER) of a storage or transmission channel may be data-dependent. This can lead to certain pathological input sequences, for which the reliability of the system is below specifications. Guided scrambling is a well-known technique to randomize the input to a channel while minimizing a certain objective function. In this paper, we take the average predicted BER as the objective function. We show that for a certain scrambling code C, for any input sequence m there exists a scrambling codeword c∈C such that the predicted BER of the (modulo-2) sum of m and c is not more than that for random input data. We present examples of scrambling codes for two-dimensional optical storage and indicate a way of combining them with error-correcting codes. View full abstract»

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  • An investigation of the effects of media characteristics on read channel performance for patterned media storage

    Publication Year: 2005 , Page(s): 4327 - 4334
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB) |  | HTML iconHTML  

    Many view data storage on patterned magnetic media as one way of attaining storage densities in excess of 1 Tb/in2 and thus overcoming the problems associated with recording at ultrahigh densities on conventional continuous media. In this paper we investigate, through the use of a replay simulation developed to take into account the three-dimensional nature of the patterned media, the effects that the shape-constrained media have on the bit-error-rate performance of the read channel in 1-Tb/in2 perpendicular recording. In particular, we analyze how media configurations with varying island shape, size, and distribution affect the channel performance. View full abstract»

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  • Iterative reduced-state decoding for coded partial-response channels

    Publication Year: 2005 , Page(s): 4335 - 4337
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    The conventional iterative decoding based on the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm rises exponentially in terms of channel memory length. In this paper, we propose a low-complexity soft-input/soft-output (SISO) channel detector based on tentative hard estimates fed back from the outer decoder in the previous iteration. The computational complexity of the proposed detector is polynomial in terms of the channel memory length. To demonstrate the performance/complexity tradeoff of the proposed detector, we present simulation results for 9-tap, 11-tap, and 12-tap channels. We show that the proposed detector significantly reduces the computational complexity with only slight performance degradation compared to the full-complexity BCJR algorithm. View full abstract»

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  • Parity-check codes and post-processing for d=1 optical recording channels

    Publication Year: 2005 , Page(s): 4338 - 4340
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    We have developed an advanced detection approach with parity-check (PC) codes and post-processing for optical recording channels. In seeking the advanced detection approach, we investigated different types of PC codes, existing as well as new. We developed a novel remedy scheme to minimize the miscorrection of error events that are split across codeword boundaries. Simulation shows that the performance of the developed PC codes approaches the corresponding bit-error-rate bounds, at both nominal density and high density. View full abstract»

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  • Interaction effect on switching behaviors of paired "Pac-Man" array

    Publication Year: 2005 , Page(s): 4341 - 4343
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB) |  | HTML iconHTML  

    Interactions between neighboring cells become increasingly important due to the miniaturization of magnetoelectronic devices. This paper studies the effect of magnetic interaction on the switching behaviors in two different configurations of paired Pac-man shape Permalloy elements: back-to-back and face-to-face configurations. From as-patterned state MFM images, it is observed that the face-to-face configuration is prone to form either two single domains with an antiferromagnetic configuration, one single domain with one vortex or a double vortex configuration. MOKE hysteresis loops show that the coercivity for the face-to-face configuration is smaller than the back-to-back configuration. These experimental results indicate that the back-to-back configuration has weaker interaction between the two Pac-man elements than the face-to-face configuration. We further varied the aspect ratio of Pac-man elements in the pair arrays to tune the magnetic interaction. It was found that the coercivity of pair array increased with the higher cell aspect ratio. Micromagnetic simulation was also performed to simulate the switching process for the two different configurations. Overall, the back-to-back configuration is recommended for applications that demands less inter-cell interactions. View full abstract»

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  • Calculations of impurity doping effects in CrO2

    Publication Year: 2005 , Page(s): 4344 - 4346
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    The effects of impurity doping in CrO2 have been calculated based on the Cr9O40 cluster using the method of DV-X α molecular orbital calculation. Elements (Mo, W) belonging to the same family as Cr and the ones (Zr, Ru, Sn) whose dioxides have the same crystalline structure as the rutile were selected for impurity doping. The calculated results show the large enhancements of the magnetic moment and the Curie temperature by the doping of Zr and Ru, respectively. View full abstract»

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  • Properties of side-shielded read heads in longitudinal and perpendicular recording

    Publication Year: 2005 , Page(s): 4347 - 4349
    Cited by:  Papers (5)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    Side-shielded (SS) read heads were fabricated, and their magnetic track widths were calculated and measured. The measurements in longitudinal recording show that SS heads exhibit sharper profiles compared with side-unshielded heads. To examine the effect of side shielding, we studied the dependence of the magnetic read width on write density using calculations and experiments. The calculations indicate that the SS head can reduce the skirt of the microtrack profile even at low densities, while the side-unshielded head cannot. This result was qualitatively found in an experiment. We also studied the SS effect in perpendicular recording and found better performance. The calculations predict that SS can strongly reduce the skirt of the microtrack profile even in perpendicular recording. We observed a sharper profile in an SS head compared with a side-unshielded one. 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