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Magnetics, IEEE Transactions on

Issue 2  Part 1 • Date March 1998

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Displaying Results 1 - 25 of 45
  • Asia-Pacific Data Storage Conference

    Publication Year: 1998
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    Freely Available from IEEE
  • Conference Author Index

    Publication Year: 1998 , Page(s): 489 - 490
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    Freely Available from IEEE
  • A laser noise reduction method for holographic pickup heads

    Publication Year: 1998 , Page(s): 474 - 476
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    There are several methods to avoid optical feedback and reduce laser noise in optical recording systems. However, most of them utilize high cost optical components or electronics or increase the pickup head size. Furthermore, it is difficult to fit these components into in a small package like a holographic laser module. In this paper, a simple method for avoiding feedback noise in a holographic pickup head is proposed. A single wave plate is added to the optical system to rotate the polarization of the laser feedback to be orthogonal to the emitting polarization state. Experimental results show that it is feasible and practically reduces laser noise View full abstract»

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  • Formation of non-equilibrium sputtered Cr films used in thin film HD recording media

    Publication Year: 1998 , Page(s): 346 - 348
    Cited by:  Papers (2)
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    Formation and phase transformation of non-equilibrium δ-A15 Cr thin films prepared by r.f. magnetron sputtering have been characterized. Processing parameters such as working pressure, deposition time and temperature were found to affect the formation of δ-A15 Cr films. We have demonstrated for the first time that the phase transformation of the δ-A15 Cr phase to the equilibrium α-BCC Cr phase is an irreversible, exothermic, first-order transition. Onset and peak temperatures of the transformation were determined to be 4280C and 437°C, respectively, at a heating rate of 100C/mln. Our post-deposition annealing study by X-ray diffraction further verified the occurrence of transformation View full abstract»

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  • Torque and cogging torque in sandwich type CD-ROM spindle motor

    Publication Year: 1998 , Page(s): 471 - 473
    Cited by:  Papers (4)
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    The sandwich type CD-ROM spindle motor has intrinsic dominance of manufacture and cost. This paper will propose a reference formula of torque constant Kt according to the experimental results, accounting for the mechanism of dead point, and finally introducing a design method to prevent dead point and to reduce the cogging torque View full abstract»

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  • MSR high density recording

    Publication Year: 1998 , Page(s): 438 - 443
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    This paper describes the high density recording using magnetically induced super resolution (MSR). We have used the double mask type of MSR, which consists of four layers of magnetic film. Recording and readout were performed with an optical head with a wavelength of 680 nm and NA 055. With light intensity modulation (LIM) recording, the lower limit of the mark length is approximately 0.35 μm because the limit of recording density is restricted by the recording power margin. With magnetic field modulation (MFM) recording combined with laser pulse, however, the recording power margin increases considerably, and recording density can be increased to the limit of S/N. We have performed MFM recording with NRZi modulation, under the assumption that a modulation method with a wide data window is adequate for MSR even when the shortest mark shrinks proportionally. Our results confirm the possibility of high density recording with marks as short as 0.2 μm (0.2 μm/bit). We have also verified that marks as short as 0.12 μm long are recorded, although the S/N is insufficient View full abstract»

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  • Switching behavior and noise in obliquely oriented recording media

    Publication Year: 1998 , Page(s): 384 - 386
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    Switching behavior and noise patterns due to an oblique misorientation of the easy axis of a system of noninteracting single domain particles (SDPs) has been investigated. Curvilinear nature of the head field as observed by the particle in the media has been taken into account using Monte Carlo simulation. For a heterogeneous media with a given set of half width of physical parameters in the distribution, one with an oblique misorientation angle near φ≃150, appears to cause less fluctuation noise spikes and good readout signal. Media with a broad oblique misorientation distribution leads to a correspondingly broad transition width, rough switching curve and noisy signal output View full abstract»

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  • High density optical storage based on superresolution techniques employing optical path filtering and saturable absorption

    Publication Year: 1998 , Page(s): 404 - 406
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    Optical superresolution techniques to increase the density of data storage by source and medium modifications are explained. It is shown that the light distribution at the source can be modified using a phase filter. This results in overall energy efficiency and improvement in the frequency response of the optical read-out. The frequency response of the optical readout with source modification Is good at medium and high frequencies. The technique of superresolution through source modification, and with saturable absorber in the medium is proposed View full abstract»

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  • Influence of packing density on recording media under high-speed field

    Publication Year: 1998 , Page(s): 355 - 357
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    We have studied the influence of interparticle interaction on the switching of recording media under a rapidly varying field. Two parallel particles with dipole-dipole coupling for arbitrary bond angle were treated analytically. Under a rapidly varying field, the oscillatory switching bands were observed before the static limit for small damping constant and bond angle. Interaction modifies the switching band shape but only the damping constant changes the band gap View full abstract»

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  • Application of simulation on the design of phase-change optical recording disks

    Publication Year: 1998 , Page(s): 414 - 416
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    Optical absorption and thermal conduction are the two key factors affecting temperature distribution and, subsequently, the write, erase characteristics of a phase-change optical recording disk. Therefore, by using carefully measured film physical properties of each layer, this work simulates a transient temperature profile while simultaneously considering optical absorption and thermal conduction. Through the simulated transient temperature profile, cooling-rate and reflectivity, dependence of phase-changed spot size on the laser power and laser pulse duration was observed. The proper combination of the disk structure and the associated write, erase conditions are obtained as well. A disk structure can subsequently be designed on the basis of this information. In addition, a novel dielectric layer, i.e. hydrogenated amorphous carbon (α-C:II), is simulated and compared with the disk applying conventionally used ZnS-SiO2 dielectric layers. The disk structures used herein are PC/ZnS-SiO2/GeSbTe/ZnS-SiO2 /Al and PC/α-C:H/GeSbTe/α-C:H/Al. According to those results, α-C:H film is highly promising as a dielectric layer of the phase change optical recording disk for both wavelengths of 780 and 660 nm View full abstract»

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  • Rotational magnetizations of particulate and thin film recording media

    Publication Year: 1998 , Page(s): 393 - 395
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    Magnetizations (Mx, along the direction of applied field) as functions of rotational angle (θ) for particulate and thin film recording media in various applied fields (H) were studied. M k(θ) was analyzed through the Fourier components (C n) and the corresponding phases (θn). The θn(H) curves for the increasing- and decreasing-field processes of the particulate recording medium are observed to be separated for H lower than specific values. However, this feature is not evident for the thin film recording medium. The distinction is related with the different microstructures of these two types of recording medium View full abstract»

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  • Application of micromachine technologies to hard disk drives

    Publication Year: 1998 , Page(s): 477 - 479
    Cited by:  Papers (2)  |  Patents (4)
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    We propose applications of micromachine technologies to increase the areal density of Hard Disk Drives (HDDs). The most attractive ways to increase the density are head positioning with high accuracy and ultra-low flying height of head sliders. We propose two micro actuators and a non-assembly micro structure. One of micro actuators is essential to achieve highly accurate positioning of head. The other actuator and the non-assembly micro structure are very useful to reduce flying height of sliders. We show the feasibility of these proposals by preliminary experiments View full abstract»

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  • High speed switching in magnetic recording media

    Publication Year: 1998 , Page(s): 349 - 354
    Cited by:  Papers (11)
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    The theoretical formalism behind the introduction of thermal activation into the micromagnetic approach is reviewed. The theory is introduced via an application to a single spin which shows a rapid increase of coercivity at short timescales of the order of nanoseconds. Interaction effects are shown to increase relaxation times. A model of thermally activated spin-waves is presented View full abstract»

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  • Overwritable phase-change optical disk recording

    Publication Year: 1998 , Page(s): 426 - 431
    Cited by:  Patents (2)
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    Three key technologies have overcome the cycle issue of phase-change optical disks. The interchangeability testing data for Multimedia PD by different media makers has verified the values specified in ECMA-240 which has become a worldwide standard. Wide wavelength response will extend the capacity of 120 mm phase-change optical disk to 15 GB/side View full abstract»

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  • Magneto-optical Kerr rotation of GdTbFeCo films at short wavelength

    Publication Year: 1998 , Page(s): 420 - 422
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    We used alternate sputter method to deposit GdTbFeCo alloy films. The Kerr spectra of these films are relatively flat in the wavelength range from 450 nm to 850 nm, and increased slightly below 450 nm. The Kerr angle increased with increased FeCo content in the GdTbFeCo film, and this relationship is independent of wavelength in the range from 450 nm to 850 nm View full abstract»

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  • Tuning of the trilayer D-RAD MO disk to readout with write direction field

    Publication Year: 1998 , Page(s): 444 - 446
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    The Double-masked Rear Aperture Detection (D-RAD) with write direction field enables very low crosstalk as well as high resolution. In this paper, composition and sputtering condition of trilayer magnetic films were investigated to obtain stable D-RAD readout with adequate read power margin. The method for evaluating the stability of the front mask was also investigated to achieve a sharp and uniform front mask View full abstract»

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  • Chain formation, thermal relaxation and noise in magnetic recording

    Publication Year: 1998 , Page(s): 358 - 362
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    Thermally activated processes have intrinsically stochastic, exponentially distributed waiting times. A simulation algorithm based on this property is used here to model the effect of a recording head on an initially demagnetized, thermally relaxing particulate medium. Coherent rotation of magnetization and dipolar interactions are assumed and it is found that interactions enhance transition noise and the width of the transition region View full abstract»

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  • Remote fine tracking mechanism for optical flying head

    Publication Year: 1998 , Page(s): 423 - 425
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    The usage of a galvanometer for providing fine tracking capability for an optical flying head is explored. Some potential R/W and servo problems may be created with such an approach. The source of these problems are analyzed, and a method of how to suppress these problems is proposed. The method we propose can also greatly improve the performance of the galvanometer system View full abstract»

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  • Effects of temperature and humidity on stiction behavior of laser zone textured disk

    Publication Year: 1998 , Page(s): 396 - 398
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    This study is to investigate the effects of relative humidity and temperature on contact start stop (CSS) performance. Commercially available 95 mm thin film disks with the diamond like coating were used in this paper. Disks were lubricated with Z-Dol. The coefficient of stiction was used to monitor the interaction between the head and the laser zone texture disk surface during CSS. The experimental data were investigated on the disk surface at 8%, 80% relative humidity and 5°C, 35°C, 60°C, respectively. It was found that the coefficient of stiction was well correlated with the lubricant film thickness and adsorbed water film thickness at the head/disk interface. For the Z-Dol lubricant on mechanical and laser zone texture disk, the coefficient of stiction of head/disk interface at 5°C, 8%RH was less than that of the 35°C, 80%RH. The coefficient of stiction for laser-zone-texture disks was smaller than that of the mechanical-zone-texture disks. From these results it can be seen that the lower coefficient of stiction and the longer lifetime of CSS test was obtained at optimum condition View full abstract»

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  • MR recording media: microstructure and magnetic properties

    Publication Year: 1998 , Page(s): 366 - 371
    Cited by:  Papers (1)
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    To achieve high recording areal density, it is required that future MR media have high coercivity (Hc), high coercive and remanent squareness (S* and S), low media noise and narrow track recording performance. The microstructure, which strongly affects magnetic properties, should be fully controlled in media fabrication process. The microstructural characteristics like grain size, grain separation, orientation, lattice mismatch, second phases, and stacking faults can affect intergranular magnetic coupling and media noise. The composition of ternary and quaternary cobalt alloy systems, e.g. CoCrTa, CoCrPt, and CoCrPtTa, has significant effects on magnetic performances. The underlayer design, e.g. Cr, CrVx, and CrTix, can affect lattice mismatch, stacking fault density, and other microstructural features. Stress, shadowing, preferred orientation, and c-axis alignment are four mechanisms which control orientation ratio (OR). Oriented medium has more stress-induced noise than isotropic medium has. Thin film medium with bicrystal structure has 5 dB better SNR than non-bicrystal medium. Ultra clean sputtering process (UC-process) can enhance coercivity and reduce noise. For GMR recording media, it requires Hc>3000 Oe and Mrt <0.5 memu/cm2. Media with CoCrPtTa, and CoSm/Cr design will be compared for areal density upto 10 Gb/in2. Mechanisms of high coercive force and low noise in MR media are reviewed in connection with microstructure and magnetic properties View full abstract»

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  • Structure and MO Kerr effect for MnSbM (M=Pt,Au,Pd) films

    Publication Year: 1998 , Page(s): 447 - 449
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    The MO (Magneto-Optical) Kerr effect for the Mn51Sb43M6 (M=Pt, Au and Pd, and Mn:51at%, Sb:43at% and M:6at%) films was discussed from the viewpoints of the structure and dielectric tensor analyses. It was clarified; (1) The Mn51Sb43M6 films after annealing at 300°C were found to consist of MnSb with the hexagonal phase and MMnSb with the f.c.c. phase. (2) The volume fraction of MMnSb with the f.c.c. phase, Vf.c.c, in the MnSbM film annealed at 300°C was significantly more than estimated value. (3) The off-diagonal part of dielectric tensor, εxy', of MMnSb with the f.c.c. phase played a dominant role in the MO Kerr effect View full abstract»

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  • In-situ n & k phase compensation in an interferometric flying height tester

    Publication Year: 1998 , Page(s): 459 - 461
    Cited by:  Papers (3)  |  Patents (5)
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    Conventional multiwavelength flying height testers rely upon an external ellipsometer for measurement of the slider's n and k. These values are used to correct the phase offset of the interferometric signal. Typically n and k measurements obtained from a sampling of 20 to 30 sliders are averaged and the results are used indefinitely in production testing. This approach to n and k phase correction may be adequate for high flying heights but it becomes less attractive as flying heights decrease and the correction becomes a large fraction of the nominal. In the new method described here phase offset is measured when a standard retract or rpm calibration is performed. Using the calibration data, an estimate is obtained of the absolute reflectivity of the slider. Next the value of the real part n of the complex index of the slider is inferred from an independent correlation of n to the slider reflectivity. Given these two numbers-the slider reflectivity R and the real part n of the index-the phase correction for flying height is calculated using a well-known relationship giving phase shift on reflection as a function of n and R View full abstract»

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  • A DSP based hard disk drive servo test stand

    Publication Year: 1998 , Page(s): 480 - 482
    Cited by:  Papers (3)
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    The paper reports the development of a hard disk drive (HDD) servo test stand developed to demonstrate the principles of a hard disk drive servo system for teaching and research. The test stand consists of a servo written head disk assembly, electronic circuits to process the HDD signal to obtain position information, a 16-bit digital signal processor (DSP) and a spindle motor controller. Hard disk drive servo control related internal signals such as the read signal, peak detector output, servo gate and servo bursts are made available for probing. A host PC is used for down loading commands and controller parameters to the DSP and up-loading the results of the servo system for display and post-processing. Implementation results of a PTOS servo controller and system identification are presented View full abstract»

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  • Magnetic force microscopy studies of DC erasure in a 5 Gbit/in2 medium [CoCrPtTa/CrMo]

    Publication Year: 1998 , Page(s): 363 - 365
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    The DC erasure process in a 5 Gbits/in2 medium is investigated using magnetic force microscopy (MFM). 50 to 250 kfci patterns were imaged in the remanent state after application of in situ magnetic fields perpendicular H and parallel H| to the tracks. Degradation of bits is observed to start at the track edges and the transitions. Decay at the transition tends to occur locally at many places and propagates into the bits with opposing magnetization relative to H|. For H, decay occurs on both sides of the transition and the written bits persist at higher fields compared to the application of H|. For the H | case, the averaged MFM signal for 50 to 250 kfci patterns fits the bulk DC demagnetization curve suggesting the reduced effect of demagnetizing fields View full abstract»

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  • Effects of initialization conditions on erasability of phase change optical disks

    Publication Year: 1998 , Page(s): 435 - 437
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    Effects of initialization conditions of initialization power and number of initialization cycles on the recording properties of phase change optical disks were studied. It is found that initialization conditions affect erasability but have little effect on carrier-to-noise ratio of phase change optical disks. The initialization conditions also affect bias power margin. Erasability of more than 20 dB and carrier-to-noise ratio of 54 dB with 4 mW bias power margin were obtained by applying 6 mW of initialization power and 5 initialization cycles 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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Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology