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Magnetics, IEEE Transactions on

Issue 5  Part 1 • Date Sept. 2002

 This issue contains several parts.Go to:  Part 2 

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Displaying Results 1 - 25 of 485
  • Magnetic relaxations in metallic multilayers

    Publication Year: 2002 , Page(s): 2496 - 2501
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    The intrinsic damping mechanism in metals caused by incoherent scattering of itinerant electron-hole pair excitations by phonons and magnons will be reviewed. The unique features of magnetic relaxations in multilayers were studied by ferromagnetic resonance (FMR) using magnetic single, Au–Fe–GaAs(001), and double layer Au–Fe–Au–Fe–GaAs(001) structures prepared by molecular beam epitaxy. The magnetic relaxation in single-layer films is described by the Gilbert damping with no extrinsic contributions to the FMR linewidth. These films provided an excellent opportunity to investigate nonlocal damping. The main result of these studies is that ultrathin Fe films in magnetic double layers acquire an additional interface Gilbert damping. This is in agreement with recent predictions of nonlocal interface damping which is based on the transport of spin angular momentum between the ferromagnetic layers. Measurements of the nonlocal Gilbert damping offer a possibility to carry out quantitative studies of the relaxation torques caused by nonlocal spin momentum transfer. Numerical simulations of magnetization reversal and stationary precession for an applied perpendicular current in Au–Fe–Au–Fe–GaAs(001) multilayers will be shown. View full abstract»

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  • Domain wall propagation on nanometer scale: coercivity of a single pinning center

    Publication Year: 2002 , Page(s): 2583 - 2585
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    Nanometer-scale movements of domain walls in uniaxial garnet films have been studied by means of micromagnetization measurements using miniature gold and semiconductor Hall probes. The high spatial resolution is achieved due to low intrinsic noise of semiconductor ballistic Hall microprobes. At low (helium) temperatures, the domain walls are found to move by discrete jumps, which we attribute to pinning on isolated defects, and we were able to measure local hysteresis loops associated with pinning on individual pinning centers. The temperature dependence of the coercive field of a single pinning center allowed us to evaluate the characteristic energy and characteristic volume of the pinning center. At higher temperatures, the character of domain wall propagation changed, and walls were found to move not only by jumps between pinning centers but also via elastic bending. View full abstract»

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  • Enhanced tunnel magnetoresistance by hf-layer insertion in the AlO/sub x/ tunnel barriers

    Publication Year: 2002 , Page(s): 2706 - 2708
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (186 KB) |  | HTML iconHTML  

    The effects of Hf-layer insertion in the AlOx tunnel barrier on tunnel magnetoresistance (TMR) are studied, and we have modified the oxide barrier by forming Hf??Al-oxide materials in the middle of Al oxide. Junctions with Hf-inserted barriers show higher TMR ratio and weaker temperature dependence than those with the conventional Al-oxide barrier. From the analysis of temperature dependence, it was concluded that the enhancement of TMR by the introduction of an Hf layer was due to the reduction of defects in the barrier. View full abstract»

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  • Magnetoresistance of MnFeP/sub 0_55/As/sub 0_45/

    Publication Year: 2002 , Page(s): 2753 - 2754
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB) |  | HTML iconHTML  

    We have measured the dependence on magnetic field and temperature of the electrical resistance and magnetization of MnFeP0.55As0.45, which undergoes a reversible first-order ferromagnetic-to-paramagnetic phase transition at a critical temperature Tcr = 231 K. The electrical resistance R(T) measured by cooling to low temperatures in zero magnetic field has a usual metallic character. The isothermal magnetic-field dependence of the magnetoresistance from 243 K to 265 K indicates the presence of temperature-dependent critical magnetic fields that transform the paramagnetic phase into the ferromagnetic phase. The critical-magnetic-field diagram determined from the isothermal magneticfield dependencies of the electrical resistance of MnFeP0.55As0.45 shows that the field hysteresis is about 1 T between the increasingand decreasing-field cycles. View full abstract»

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  • Characteristics of cobalt-doped zinc oxide thin films prepared by pulsed laser deposition

    Publication Year: 2002 , Page(s): 2880 - 2882
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (214 KB) |  | HTML iconHTML  

    We have characterized Zn1–xCoxO thin films grown on sapphire (0001) substrates by pulsed laser deposition. We have found for x = 0.25 that inhomogeneous Zn1–xCoxO films with wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases are formed when the growth temperature (Tg) is relatively high (⩾600 °C) and the O pressure (Po2) is fairly low (⩾10–5 torr). The presence of the Co clusters leads to room temperature ferromagnetism. Homogeneous Zn1–xCoxO alloy films with wurtzite structure are predominantly paramagnetic. High-quality epitaxial Zn1–xCoxO alloy films are formed at a growth condition of Tg= 600 °C and Po2 = 10–5 torr. Under this optimized growth condition, Co can be dissolved into ZnO up to around 40%. Photoluminescence spectra and electrical properties of Zn1–xCoxO strongly depend on the Co content. View full abstract»

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  • The FMR behavior of an ultrathin single Fe layer on a GaAs substrate

    Publication Year: 2002 , Page(s): 3117 - 3119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (350 KB) |  | HTML iconHTML  

    Single-layer Fe films 800 Å thick, with and without a 10-Å-thick Ag buffer layer, were prepared at various growtht emperature,Tg, on GaAs(001) substrates by molecular-beam epitaxy. For Tg around 200 °C, high-quality single crystal films were obtained without the Ag buffer layer. For Tg ⩽100 °C, a defect structure was observed in the iron layer. However, the addition of an ultrathin Ag buffer layer between GaAs and Fe has the desirable effects of eliminating the defect structure and significantly enhancing the FMR absorption. View full abstract»

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  • Conference Author Index

    Publication Year: 2002 , Page(s): 3386 - 3394
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    Freely Available from IEEE
  • 2002 International Magnetics Conference INTERMAG 2002

    Publication Year: 2002 , Page(s): 1841 - 1857
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    Freely Available from IEEE
  • Radial error propagation issues in self-servo track writing technology

    Publication Year: 2002 , Page(s): 2180 - 2182
    Cited by:  Papers (15)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (298 KB)  

    Conventional servo track writing needs external devices to position heads in hard disk drives to write servo patterns. In self-servo track writing (SSTW), the position reference is regenerated from previous written tracks and a servo pattern is propagated to cover the disk in a progressive mode. Errors will propagate and compound in this process. In this paper, the radial error propagation is discussed and a containment scheme is established. Furthermore, experimental results of SSTW on a head-disk assembly with blank media and off-the-shelf electronics are analyzed to show the effectiveness of error containment in self-radial propagation. View full abstract»

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  • Dual-stage servo with on-slider PZT microactuator for hard disk drives

    Publication Year: 2002 , Page(s): 2183 - 2185
    Cited by:  Papers (11)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    A dual-stage servo system with an on-slider piezoelectric (PZT) microactuator is developed for future high-density hard disk drives. The parallel control scheme is used in servo design with considerations over the stroke limitation and the hysteresis of the microactuator. Experimental results on a spin-stand with a laser Doppler vibrometer as the position sensor demonstrate that the system has a servo bandwidth higher than 4 kHz and has disturbance rejection capability up to near 5 kHz. View full abstract»

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  • Design and analysis of a new multiphase polygonal-winding permanent-magnet brushless DC machine

    Publication Year: 2002 , Page(s): 3258 - 3260
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (214 KB) |  | HTML iconHTML  

    In this paper, a new multiphase polygonal-winding permanent-magnet brushless dc (PMBDC) machine is proposed and analyzed. The originality of the proposed machine lies on the multiphase polygonal-winding stator and the surface-inset permanent-magnet rotor. Because of its unique structure and operating principle, a circuit-field-torque coupled time stepping finite-element method is also employed for analysis. The designed machine is prototyped and the analysis is verified by experimentation. View full abstract»

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  • A highly durable structure of carbon protective layer

    Publication Year: 2002 , Page(s): 2129 - 2131
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    Mechanical durabilities of carbon protective films for recording media were investigated by pin-on-disk tests. Chemical structures of carbon films were correlated with that of underlying metal films using X-ray photoelectron spectroscopy (XPS). It was found that the chemical structure of the carbon at the initial stage of deposition was influenced by the metal underlayers, resulting in different mechanical durabilities of the media. A Pt thin underlayer for a carbon layer promoted growth of a diamond-like carbon structure from the initial stage of deposition, making strong mechanical durability. View full abstract»

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  • Multistate per-cell magnetoresistive random-access memory written at Curie point

    Publication Year: 2002 , Page(s): 2850 - 2852
    Cited by:  Papers (7)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (185 KB) |  | HTML iconHTML  

    A multistate per-cell magnetoresistive random-access memory (MRAM) that writes data by a thermally assisted technique and reads data using the angular-dependent magnetoresistance is proposed. A hard magnetic layer or pinned ferromagnetic layer (CoFe-IrMn) is used as the recording layer. The free layer serves as the read layer. Before reading, the free layer's magnetization is set to the initial state. For the N states per-cell MRAM, the magnetization angle of the ith state (i=0 to N-1) between the free layer and recording layer can be set to be acos(1-2*i/(N-1)). For example, in the four-state per-cell MRAM, the magnetization angle can be set to be acos(1), acos(1/3), acos(-1/3), and acos(-1), which represent the four states, respectively. More states can be obtained if the signal-to-noise ratio is sufficient. At near Curie point, a small external field can be used to record the signal. In order to verify the idea, a spin-valve giant-magnetoresistance memory cell was fabricated using e-beam lithography and ultrahigh voltage sputtering. A 25-mA heating current and a small external field are enough to assist the writing process. A four-state per-cell memory is realized by this method. View full abstract»

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  • Design criteria for detent force reduction of permanent-magnet linear synchronous motors with Halbach array

    Publication Year: 2002 , Page(s): 3261 - 3263
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    In order to improve power efficiency, Halbach magnetized topology is applied to a short secondary slotted permanent-magnet linear synchronous motor (PMLSM). Detent force of slotted PMLSMs is due to the interaction between the edges of the permanent magnet and the teeth of the primary core. This paper deals with detent force reduction methods such as adjustment of magnet length and skewing. Reduction effect of detent force and thrust performance for two topologies are also compared. View full abstract»

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  • Spatial effects in the dc modulation noise of advanced MP tape

    Publication Year: 2002 , Page(s): 1904 - 1906
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    An experimental study of dc modulation noise as a function of the remanent magnetized state has been made for a set of advanced metal particle tapes with identical particles but different magnetic coating thickness between 150 and 300 nm. The thickest tape showed noise characteristics similar to conventional thick tapes, whilst the noise spectrum of the thinnest was "thin-film" like. A simulation of a magnetic recording head-read process has been developed and applied to a model of particulate recording media. This showed that particles at the surface contribute noise characteristics similar with those of thin films, whereas noise from particles in the bulk is characteristic of thick media. As tapes get thinner, the noise is dominated by the characteristics of the particles on the top surface. View full abstract»

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  • Experimental correction of the axial shielding equation

    Publication Year: 2002 , Page(s): 3324 - 3326
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    The conventional analytical description of axial shielding for cylindrical shields is based on the assumption that the field reduction inside the shield is due to the demagnetizing field within the equivalent ellipsoid. It seems more reasonable, however, to employ in the axial shielding equation the demagnetizing factor calculated for the equivalent rod, because the shields analyzed have the same outer surface as the rod does. In order to support the above idea experimentally, we built and investigated cylindrical shields having different aspect ratios. The permeability of the shielding material was controlled at a number of levels by magnetic shaking. The results obtained show a good agreement between the experimental and new analytical data. View full abstract»

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  • Erase and write widths for narrow track high-density flexible storage media applications

    Publication Year: 2002 , Page(s): 1913 - 1915
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB) |  | HTML iconHTML  

    A detailed study of the magnetic widths of data tracks recorded in metal particle media is reported. These widths are important in determining the track density of future flexible media storage systems. The tracks were written using a novel inverted write head that offers excellent pole width tolerance control. The widths of both the written track and erase zone were studied as functions of both write current and write head dimension. It was found that the erased track widths written with both the wide and narrow poles were very similar and increased with increasing write current. However in the case of writing with the wide pole, the written track widths increased with write current whereas those written with the narrow pole did not. This was interpreted as resulting from a curved fringing field whose width increases with write current. Variation of the throat height was not found to significantly affect the width of tracks written with either pole. View full abstract»

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  • Magnetooptic switch based on domain wall motion in orthoferrites

    Publication Year: 2002 , Page(s): 3243 - 3245
    Cited by:  Papers (16)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB) |  | HTML iconHTML  

    A prototype of an optical switch based on Faraday rotation in yttrium orthoferrite crystals is developed. The switch is of latching type and has an operating time below 100 ns. Integrated arrays of switches are feasible due to the dimensions of the optical rotator of less than 3 mm3. View full abstract»

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  • Magnetization estimation from MFM images

    Publication Year: 2002 , Page(s): 2444 - 2446
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB) |  | HTML iconHTML  

    We have developed a method to estimate the complete magnetization in thin-film longitudinal recording media from magnetic force microscopy (MFM) data. The method uses a medium model described by a Voronoi tessellation of the film plane. The magnetization lies in that plane, has constant magnitude, and is uniform within each convex region, or grain, of the tessellation. The effect of a single grain on the MFM simulation is isolated by considering the difference between the MFM images before and after that grain undergoes a 180° magnetization reversal. Using this difference image, the complete magnetization of the grain and the grain's boundaries are estimated. By isolating each grain in turn, as if a series of incremental applied fields had been applied, the magnetization for the whole pattern is estimated. View full abstract»

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  • Comparison of two types of PM linear synchronous servo and miniature motor with air-cored film coil

    Publication Year: 2002 , Page(s): 3264 - 3266
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    Permanent-magnet linear synchronous motors (PMLSMs) with air-cored film coil are applied to servo, miniature, and precision motion-controlled linear machines. On the basis of analytical field solutions, this paper deals with the comparison of the design guidelines, magnetic field, winding electromotive force, required magnet volume, optimal winding thickness, and thrust force for two types of permanent magnet movers. View full abstract»

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  • Birefringence of magnetite-based magnetic fluids: the effect of the surface-coating layer

    Publication Year: 2002 , Page(s): 3228 - 3230
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (179 KB) |  | HTML iconHTML  

    Water-based and hydrocarbon-based magnetic fluids (MFs) containing Fe3O4 nanoparticles are investigated using static magnetic birefringence measurements. A strong dependence of the birefringence signal upon the magnetic permeability is found. In addition to the field dependence of the magnetic permeability, inclusion of dimers in the description of the birefringence signal yields excellent agreement between parameters obtained from birefringence and high-resolution microscopy data. View full abstract»

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  • Magnetic properties of acicular ultrafine iron particles

    Publication Year: 2002 , Page(s): 1907 - 1909
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    Magnetic properties of acicular (∼60 and ∼200 nm) iron particles, obtained by reduction of alumina-coated goethite particles, are reported. X-ray diffraction and Mossbauer spectroscopy showed that the particles consist of an α-Fe core and a thin surface layer of maghemite. Magnetization data indicated an improvement of ∼28% in the saturation magnetization, coercive field, and squareness for particles with ∼60 nm. This magnetic property enhancement of the present particles, whose size is 40% smaller than those commercially available, could result in a similar decrease of the bit-size for higher density of magnetic media. View full abstract»

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  • Power transmission of a desk with a cord-free power supply

    Publication Year: 2002 , Page(s): 3329 - 3331
    Cited by:  Papers (29)  |  Patents (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    The battery is an indispensable component of portable electronic equipment, but charging is often inconvenient. A contactless electric power supply, such as the desk-type contactless power station (CLPS) we propose, significantly improves the ease of charging such equipment. In this system, primary coils are embedded into the desk surface to efficiently supply electrical power to portable equipment placed on the desk. Only the primary and the secondary coils facing each other work as a power transmitter. We have confirmed that electric power transmission with efficiency of 85 ± 5% can be attained anywhere on the desk. This examination reveals the effectiveness of using several primary coils. View full abstract»

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  • Discrimination of multiple sources of alpha brain activity with 3-D MEG measurement

    Publication Year: 2002 , Page(s): 3344 - 3346
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    We carried out measurement of magnetic alpha waves using a 195-channel whole-head vector magnetoencephalogram (MEG) system for detecting three magnetic field components Br, Bθ, Bφ. In order to discuss multiple sources of the magnetic alpha wave, a source-estimation algorithm with singular value decomposition (SVD) was used. The SVD method was applied to spatio-temporal data with time window of every 100 ms, and two dominant singular values were obtained for each of the three components. Two singular values with score proportion > 80% were also obtained for both the right and the left hemisphere. With an isofield contour map of the tangential component of the magnetic alpha wave, two extreme values existed. Tangential components (Bθ, Bφ) with SVD were useful for discriminating multiple sources of magnetic alpha waves overlapping in time rather than using only the radial component Br. View full abstract»

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  • The structural and magnetic characterization of molecular-beam-epitaxy-grown FeMn-NiFe exchange-biased bilayers

    Publication Year: 2002 , Page(s): 2758 - 2760
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (203 KB) |  | HTML iconHTML  

    Structural and magnetic characterizations have been performed on NiFe-FeMn exchange-biased bilayers grown by molecular beam epitaxy. The growth of the films showed high-quality epitaxy with well-defined flat interface between the layers. Magnetic measurements confirmed that the films showed not only a comparable exchange anisotropy field (Hex) to that of sputtered films but also a lowered threshold thickness of 2 nm at which Hex vanishes for the FeMn. 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