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Magnetics, IEEE Transactions on

Issue 5 • Date September 1986

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Displaying Results 1 - 25 of 318
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Multilayer films of CoCrTa for perpendicular recording media

    Page(s): 328 - 330
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    Multilayer structures of alternate magnetic and non-magnetic CoCrTa alloys have been prepared in which the magnetic properties can be widely varied by changing the magnetic layer and interlayer thicknesses, In this way, one example has shown that enhanced perpendicular anisotropy can be achieved as demonstrated by an increase in perpendicular coercivity Hc(perp) and a decrease in longitudinal coercivity Hc(&dlor.). This condition is desirable for application in perpendicular recording media. In addition, a second example has shown that by using much thinner layers (≃15 nm) it is possible to produce a structure in which the magnetization is longitudinal with a very low coereivity of 1.5 Oe. Such soft magnetic films with high Ms and low Hc(&dlor.) can be used as underlayers for perpendicular recording media in order to enhance the efficiency of pole heads. View full abstract»

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  • The role of atomic mobility during film growth in the structural and magnetic properties of CoCr

    Page(s): 331 - 333
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    We have studied the morphological, crystallographic, and magnetic properties of CoCr thin films sputtered at different substrate temperatures and pressures. Conditions which produce high adatom mobility on the surface of the growing film lead to good c-axis orientation and magnetic anisotropy normal to the substrate, while low mobility leads to poor c-axis orientation and anisotropy. These results are explained in terms of van der Drift's model of the evolutionary growth of vapor-deposited films. The perpendicular coercivities of our samples depend only on the substrate temperature and we find no correlation with the film morphology or grain size. View full abstract»

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  • New longitudinal recording media CoxNiyCrzfrom high rate static magnetron sputtering system

    Page(s): 334 - 336
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    Three new magnetic alloys A:Co64.2Ni27.4Cr8.4. B:Co74.1Ni15.9Cr10.0, and C:Co82Ni18were used as targets to sputter thin films with coercivities up to 1015 Oe, 926 Oe, and 825 Oe respectively. Chromium films were used as the base layer. With a base pressure below 2 × 10-7torr and chromium thickness of 2500Å, the following magnetic characteristics of alloys A and B were obtained: Hc>900 Oe, Brδ>530 G-µm, S>78%, S* > 93%, S/N (at 5MHz) > 45dB and D50> 17KBPI. X-ray diffraction measurements indicate the (1011) texture of CoNiCr films is the reason for the high coercivity and squareness ratio. This orientation may result because the in-plane atom density for Co alloys HCP(1011) and Cr BCC View full abstract»

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  • Magnetic properties of evaporated CoCr films

    Page(s): 337 - 339
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    Perpendicular magnetic CoCr films were prepared on glass substrates using electron beam evaporation. The magnetic properties depend strongly on the substrate temperature, Ts. The anisotropy field,H_{k}^{eff}, and the perpendicular coercivity, Hc(perp) show maximum values at Tsaround 250°C. In this case, the alignment of c-axis is optimal and the grain size is smallest. The lattice spacing of the c-planes increases wlth Tsuntil 300°C. When the films prepared below 200°C were annealed around 300°C in high vacuum, the saturation magnetization, Ms, increased. The value of Ms, however, decrease by annealing above 400°C. In spite of the decrease of Msdue to the annealing above 400°C,H_{k}^{eff}and Hc(perp) increase by annealing above 400°C. If the films were bombarded by argon ions during film growth, Msdecreased and the internal stress changed from tensile to compressive. For low substrate temperature (below 150°C),H_{k}^{eff}decreased due to ion bombardment. View full abstract»

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  • Corrosion behavior of CoCr films in Sulfuric acid

    Page(s): 340 - 342
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    The corrosion behavior of CoCr films (∼500 to 1000 nm thick) deposited on glass by RF sputtering has been examined by classical electrochemical methods which provide a simple and rapid means for comparing one material with another. The development of a specially designed holder to allow electrical contact to the film and exposure to a sulfuric acid electrolyte was required. A comparison of potentiodynamic polarization curves for films containing various amounts of Cr with similar data from the literature for bulk CoCr alloys showed analogous behavior in the shape of the curve and in the level of Cr required to produce passivity, about 15-17%. Results indicate the formation of a passive layer containing a chromium oxide. In addition, comparison of an as-received sample with an electrochemically treated sample using Auger electron spectroscopy along with polarization results showed that Co oxides are apparently stabilized by the presence of Cr. Auger results also suggest that corrosion and passivation occur along the spaces or crevices between columnar grains during electrochemical treatment as indicated by the presence of a significant oxygen content. View full abstract»

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  • Significant improvement of magnetic properties and corrosion resistance in evaporated Co-Ni recording media

    Page(s): 343 - 345
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    An addition of a very small amount of Pr in Co-Ni films of a recording medium improves both corrosion resistance and frequency response. The columnar grains, which are induced by oblique incidence of evaporation, becomes remarkably finer by the addition of rare-earth elements. The TEM image of the cross section of the films shows a dense packed structure. High magnetization and a better corrosion resistance are considered to be due to the dense packed structure. The fine grain improves the frequency response. Among several rare-earth elements, especially Pr doping yields a best recording performance. View full abstract»

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  • Wear resistance, mechanical strength and microstructure on sputtered CoCr perpendicular media

    Page(s): 346 - 348
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    Wear resistance for sputtered CoCr perpendicular recording media has been investigated. Wear resistance and mechanical strength (tensile strength and Young's modulus) have been measured for CoCr (0-33 at% Cr) films deposited under various sputtering conditions. Furthermore, their correlations to CoCr film microstructures have been studied. The wear resistance on the CoCr films strongly depends upon the mechanical strength, and their relationship can be explained in terms of Archard's adhesive wear theory. Wear resistance and mechanical strength for CoCr (5-33 at% Cr) films decrease steeply at high sputtering Ar pressure. However, those for pure Co films are independent from sputtering pressure. Microstructure analyses for CoCr and pure Co films indicate that a main factor reducing the wear resistance and the mechanical strength is Cr segregation in the CoCr films. View full abstract»

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  • Wear properties of perpendicular magnetic recording media

    Page(s): 349 - 351
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    Wear properties of sputtered Co-Cr/permalloy double layer on flexible substrate with and without an inorganic protective top layer were studied under simulated tribological conditions. A soft head slider (ex. glass) gave even severer damage to media than the hard one (ex. Al2O3-TiC), and a 200 Å thin inorganic protective top layer was effective enough to enhance resistance against wear. Read-write experiments were also done with use of the double layer flexible media with the protective top layer (200 Å in thickness) by running them on a specially designed driver unit with an Al2O3.TiC spherical SPT head. An out-put signal loss was no more than 3dB even after 10 million times of the head passes. View full abstract»

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  • Magnetic properties and longitudinal recording performance of corrosion-resistant alloy films

    Page(s): 352 - 354
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    This paper describes the magnetic properties, recording performance and corrosion resistance of sputtered CoCr alloy films and CoCrTa alloy films. The saturation magnetization of CoCr was 525 emu/cc and not affected by substitution of a small amount of Ta. CoCrTa films exhibit greater coercive force values than CoCr films. The maximum coercive force of CoCrTa was 1400 Oe at a thickness of 400A, whereas at a similar thickness the coercive force of CoCr was 900 Oe. The coercive force decreases linearly with temperature (25°C. to 125°C.) at a rate of 3.16 Oe/°C. for CoCrTa and 1.87 Oe/°C. for CoCr. Longitudinal recording performance at -3 dB signal level was 8386 flux reversals/cm (21,300 fci) and 11,063 flux reversals/cm (28,100 fci) for CoCr and CoCrTa respectively. The alloys exhibited corrosion resistance at 80% relative humidity and 65° C. for a two-week period equivalent to at least six years under ambient disc drive conditions. View full abstract»

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  • An approach for deriving field equations for magnetic heads of different geometrical configurations

    Page(s): 355 - 360
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    This paper describes an approach for deriving field equations for virtually any magnetic head configuration. As an example, equations are derived for the thin-film head configuration. Results obtained from the new equations and those obtained from previously derived equations are compared to results obtained from the finite difference method. Results obtained from the new equations are also compared to data obtained from measurements on a large-scale thin-film head. View full abstract»

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  • Three dimensional write model for magnetic recording

    Page(s): 361 - 363
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    A three dimensional self-consistent write model is developed. Transitions are computed for infinite and finite pole tip narrow track heads on oriented and in-plane isotropic horizontal media. Magnetization patterns and readback on- and off-track are discussed. View full abstract»

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  • Simulation of the perpendicular recording process including image charge effects

    Page(s): 364 - 366
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    This paper presents a complete model for the perpendicular recording process in single-pole-head keeper-layer configurations. It includes the influence of the image-charge distributions in the head and the keeper layer. Based on calculations of magnetization distributions in standstill situations, the model describes the relaxation process that takes place if the activated head is shifted along the recording layer, periodically switching its head field. The magnetization distributions thus derived are used in combination with a model for the readback process to calculate the readback flux and voltage pulses. For the sake of arithmetical convenience, the model was applied to a recording configuration with a thick single-pole head, but it can also be used for calculations with other head shapes, e.g. thin single-pole heads. View full abstract»

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  • The switching criterion in perpendicular magnetic recording

    Page(s): 367 - 369
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    This paper presents a theoretical analysis of the effect of the "switching criterion", the level at which self-consistency is assumed in calculations on the perpendicular magnetic recording process. It can be proven that in a perpendicular recording configuration with an ideal keeper layer and a recording layer with a rectangular hysteresis loop, the switching criterion in stand-still recording situations is immaterial, because self-consistency is reached at all depth levels simultaneously. If either the keeper layer is absent, or the recording layer's hysteresis loop is sheared, it is shown that the higher the level at which self-consistency is assumed, the sharper the stand-still recorded transitions will be. View full abstract»

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  • Properties of one-sided probe heads on double-layer perpendicular recording media

    Page(s): 370 - 372
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    The perpendicular recording mode is still a candidate for obtaining higher densities. Best recording results on a double-layer (DL) medium must be expected from using a probe head (PH). This contribution provides an analysis of the write-read performance of one-sided PHs that do not use an auxiliary pole on the back of the medium. Analytical as well as numerical models were used to calculate the effects of saturation and medium thickness on the write fields. Experimental verification of the modeling results was obtained by measuring the wavelength response of many W-shaped PHs on DL media. Combining this with the calculated response, we obtained a semi-empirical relation between the pole nulls, pole thickness and the pole-to-backlayer distance. It reveals a PH behaviour very different from a ring head (RH). The pole thickness calculated from the measured pole-null wavelengths showed a very close agreement with the optically determined value. The calculated head efficiencies are very small, as was confirmed experimentally, and need improvement before the PH has an output comparable with a RH. View full abstract»

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  • Magnetization transitions obtained by deconvolution of measured replay pulses in perpendicular magnetic recording

    Page(s): 373 - 375
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    Magnetization transitions in perpendicular magnetic recording have been calculated from measured replay pulses by a deconvolution algorithm using an analytical expression for the field of a probe head (PH). The transitions appear to be asymmetric whereby a pronounced magnetization peak occurs whose shape depends on the medium coercivity. For the experiments double layer media with double sided probe heads have been used. For the deconvolution only perpendicular head field and medium magnetization components are considered. View full abstract»

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  • The effect of magnetic interaction between medium and head on perpendicular magnetic recording characteristics

    Page(s): 376 - 378
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    The high density recording characteristics of perpendicular magnetic recording using a single-pole head are affected by the magnetic interaction between the medium and the head. By decreasing the relative thickness of the Co-Cr layer in the double-layer medium to that of the main-pole of the head, and increasing the saturation magnetization of the Co-Cr layer, the high density recording characteristics are enhanced. When requisite conditions are realized, the reproduced voltage vs. bit density characteristics are improved considerably for a thinner main-pole of the single-pole head. View full abstract»

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  • Computer modeling of the write process in perpendicular recording

    Page(s): 379 - 381
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    A self-consistent computer simulation model utilizing a ring head and single layer recording medium has been developed to study perpendicular recording. In the model it is assumed that the medium switches uniformly following the volume averaged field. The optimum recording field obtained from the model calculation at various head-medium spacings permits an estimation of head saturation limitations. The roll-off curve, which is the linear superposition of the alternating voltage pulses, is in good agreement with experimental data. The write spacing loss is spacing dependent and is 120d/λ (dB) at contact for a typical recording case. For contact recording the imaging effect is important in the write process. Optimum recording at contact is shown to produce a high overshoot and sharp leading edge in the transition while leaving the magnetization level below the coercivity; this yields an apparent "negative" transition length in terms of the arctangent transition model. View full abstract»

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  • Transition lengths in magnetic recording on particulate disks

    Page(s): 382 - 384
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    Magnetic recording parameters including output vs. Write current, output vs. recording density and overwrite modulation vs. Write current have been measured on eight experimental disk samples of cobalt- doped gamma iron oxide using manganese-zinc ferrite heads. Transition length parameter plus head-medium separation distance values were calculated from output vs. recording density curves. Transition length was found to increase with increasing write current and with increasing record gap length for gap lengths ranging from 0.4 to 1.25 µm. Transition lengths were also found to depend on the recording medium parameters of remanent moment, coercivity, S* and thickness. Minimum values of transition length were found to occur at write current levels insufficient to obtain adequate overwrite modulation. View full abstract»

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  • Analysis due to vector magnetic field for recording characteristic of metal evaporated tape

    Page(s): 385 - 387
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    Metal-evaporated tape (ME tape) is one of the most promising materials for high-density magnetic recording. In a previous study, we reported that the recording characteristics of ME tape are directly affected by the columnar microstructure of the magnetic layer (Co-Ni-O magnetic film). In this study, we have conducted the theoretical analysis of the effects of both head motion and the vector magnetic field Hθ, which is essentially parallel to the columnar longitudinal axis. The results of this analysis offer an effective explanation of the recording characteristics of ME tape. View full abstract»

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  • Theoretical Comparison of readback harmonic responses for longitudinal recording and perpendicular recording with probe head over a medium with permeable underlayer

    Page(s): 388 - 390
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    In this work we compare the theoretical readback harmonic responses of longitudinal and perpendicular recording with ideal two-dimensional heads which have infinite permeable cores. The comparison provides a clear picture of the difference between the readback performance of longitudinal and perpendicular recording. View full abstract»

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  • The dynamic vectorial model for assemblies of acicular particles

    Page(s): 391 - 393
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    We use the Landau-Lifshitz equations to construct a dynamic model for describing a system of interacting particles. The dynamic model will produce results different from the static model for a finite line of particles with weak interaction strength and parallel anisotropy axes at a large angle to the line. Small two and three dimensional clusters of particles are also discussed. All the results indicate that increasing the angular distribution of the particles will reduce the difference between the static and dynamic simulations. The dynamic switching model is necessary for perpendicular recording because of the alignment of the switching units in the perpendicular media. View full abstract»

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  • Shear-sensitive magnetoresistive robotic tactile sensor

    Page(s): 394 - 396
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    We have developed a tactile sensor for robotic applications that is sensitive to pressure and, unlike most other tactile sensors, also responds to shear components of the vector force. We consider this an important advantage for robotic manipulation. In our design a magnetoresistive detector senses variation in the magnetic field of a miniature magnetic joystick. This joystick is mechanically mounted by attaching it to a metal foil, which provides elasticity without hysteresis. The detector chip is fabricated using IC technology, and an array of joystick mechanisms can potentially be made by batch processing. We have designed and partially tested a 2 × 2 array prototype, demonstrating the viability of this approach. View full abstract»

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  • Detections of secondary current and torque of induction motors using amorphous microcore field sensors

    Page(s): 397 - 399
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    New secondary-current sensors for squirrel-cage induction motors are presented using a multivibrator with two group amorphous microcores. The 8-pair micro cores are set near the both endrings of a rotor for cancellation of the influence of unstable rotor motion on sensing of the secondary current. Electromagnetic torque was detected as an output voltage of a multiplier for the secondary current and the main flux. The main flux was detected using a multivibrator-type flux sensor utilizing two stator teeth as two cores. A possible new control system for variable speed induction motors with a torque feedback loop is discussed, which stably works independently of variations of motor parameters. View full abstract»

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  • Numerical analysis and experimental study of the error of magnetic field strength measurements with single sheet testers

    Page(s): 400 - 402
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    The error of the measurement of the magnetic field strength with a single sheet tester has been studied. Two different methods, determination by means of field sensing coils (1) and from the magnetizing current (2), have been compared. The errors of methods(1) and (2) were calculated by the finite element method (FEM), different parameters having been varied, and method (2) was additionally studied experimentally. SSTs with wound yokes and stacked yokes were considered. The results will help to decide whether the more complicated and more accurate H coil method or the easier to handle, but less accurate m.c.method is chosen. View full abstract»

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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