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Magnetics, IEEE Transactions on

Issue 5  Part 1 • Date Sept. 1997

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Displaying Results 1 - 25 of 279
  • Preparation and magnetic properties of Fe-Ti-N thin films

    Page(s): 2851 - 2853
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    In this paper the dependence of the magnetic properties of Fe-Ti-N thin films on partial nitrogen pressure (PN2/PTotal) during sputtering were studied. Fe-Ti-N thin films were prepared with a dc magnetron reactive sputtering apparatus, using a composite type of target in Ar and N2 mixed gas. The crystal structure and magnetic properties of the films were investigated. A single α-Fe (110) peak appeared at various partial nitrogen pressure (PN2/PTotal). When PN,sub>2/PTotal was increased, the width of α-Fe (110) peak became broader. The α-Fe (110) peak shifted to lower angle direction, and the maximum value of the lattice constant was about 2.93 Å at PN2/PTotal in the range of 2.5 ~ 5 %. The value of coercivity (Hc) was 26 Oe, and the value of the saturation magnetization (Ms) was about 1400 emu/cc at PN2/PTotal of 0 %. The minimum value of Hc was 2.4 Oe at easy magnetization direction, and 1.35 Oe at hard magnetization direction at PN2/PTotal of 2.5 %. The Ms of films increased at PN2/PTotal in the range of 2 ~ 5 %. Soft magnetic properties were obtained at PN2/PTotal of 2.5 %. View full abstract»

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  • Damping constants of Co-Cr-Ta and Co-Cr-Pt thin films

    Page(s): 2989 - 2991
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    Gilbert's damping constants, α , of Co-Cr-Ta and Co-Cr-Pt thin films are determined by Q-band FMR analysis using single crystal magnetic thin films epitaxialIy grown on MgO(110) substrates. α is calculated from the resonance width of the FMR spectrum. α of Co77Cr19Ta4 is found to increase from 0.016 to 0.028 as magnetic layer thickness increases from 25 to 240 nm. α also increases from 0.009 to 0.019 when the Cr concentration in the 60 nm thick Co96-x CrxTa4 magnetic layer is increased from 8 to 19 at.%. The 25 nm thick Co81Cr15Pt4, film has a 2.5 times larger α value (0.038) than the Co81Cr15Ta4 film (α = 0.014) with the same thickness. View full abstract»

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  • Simulation of magnetooptical domain boundary images

    Page(s): 3274 - 3276
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    Simulated magnetooptical images of domain walls are compared quantitatively with direct observations. The simulation is based on a micromagnetic model of V-lines in (110) oriented iron, a linear theory of magnetooptical diffraction and image formation based on Fourier optics. View full abstract»

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  • Conference Author Index

    Page(s): 3463 - 3472
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    Freely Available from IEEE
  • A reactive ion milling process for patterning narrow track iron nitride recording head poles at the wafer level

    Page(s): 2830 - 2832
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    A thin metal mask is desirable when defining narrow structures by ion milling. This article explores the definition of narrow high moment iron nitride inductive head pole structures by ion milling in Ar/O2 and Ar/N2 gas environments through a Ti mask. Modest ion milling selectivities between Ti and the iron nitrides (FeAlN and FeTaN) were achieved by ion milling in Ar/O2, although the mill rate of the iron nitrides was reduced dramatically. Selectivities of over 4 were achieved by ion milling in Ar/N2 ambient, without severely reducing the ion milling rates of the iron nitrides. Hence this reactive mill process is a viable method for defining narrow iron nitride poles by ion milling at the wafer level View full abstract»

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  • Feedforward noise canceller for PR1ML

    Page(s): 2800 - 2802
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    We present the performance of a feedforward noise canceller (FNC) for the PR1 [(1+D)] channel combined with an 8/10 DC free code. It appears the PR1 channel can be superior to PR4 [(1-D)(1+D)] and EPR4 [(1-D)(1+D)2] for high density magnetic recording due to a characteristic of high frequency suppression. Simulation results show that PR1 with FNC is better than EPR4 for K⩾2.5 [K=PW50/T]. We adapted PR1 with FNC into an actual DDS3 (Digital Data Storage 3) system and we got an improved result. Applying FNC to DDS3 system can improve the error rate by around 102 View full abstract»

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  • Magnetic stability and noise characteristics of high Hc CoSm/Cr thin films

    Page(s): 2977 - 2979
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    The effects of exposure time, annealing temperature and mechanical stress on the magnetic stability of CoSm/Cr thin films, as well as its noise characteristics, were studied. The coercivity (He) of the films decreases with time because the Sm is oxidized. This change is reduced by means of a protective over coat. With an annealing temperature increase, the Hc of Cr/CoSm/Cr film decreases. From Extended X-ray Absorption Fine Structure (EXAFS) analysis, it has been shown that the proportion of the Co5Sm phase increases after annealing at 250°C. Also, the Hc of the films increases with increasing compressive strain. The value of the change is about 3 times the value reported for CoPt. A low noise level and a high S/N at 97 kfci is obtained by weak exchange coupling caused by the increase in Ar gas pressure during Cr sputtering View full abstract»

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  • Microscopic magnetic characterization of submicron cobalt islands prepared using self-assembled polymer masking technique

    Page(s): 3022 - 3024
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    Patterns of submicron cobalt islands were created on silicon by using self-assembled co-polymers as etching masks. The synthesis conditions were varied to create specific magnetic island morphologies. The magnetic structure and magnetization reversal of interconnected, as well as interacting and non-interacting islands were systematically studied using magnetic force microscopy. Differences in magnetic characteristics were observed and correlated with the thin film morphologies. The result of these studies include the transition from single to multidomain configuration as a function of island size, domain boundary characteristics near coercivity, evidence of magnetization rotation with increasing reverse magnetic field, and evidence of collective switching behavior in interacting single domain islands View full abstract»

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  • Design of high density dual stripe MR heads using a thermal transmission line model

    Page(s): 2920 - 2922
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    A thermal transmission line model is described and used to study the performance of high track density dual stripe magnetoresistive (DSMR) recording heads. The model was calibrated to actual thermal and signal amplitude data by adjusting sensor material properties. Signal sensitivity per unit track width from the preamp are shown to improve by decreasing the sensor thickness. Further improvement with track density is predicted for smaller aspect ratios. For a square active region (aspect ratio =1.0) no degradation in signal sensitivity was seen up to approximately 19 ktpi View full abstract»

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  • Longitudinal-transverse linear transformation of the HF-current in soft magnetic materials with induced anisotropy

    Page(s): 3367 - 3369
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    Excitation of HF axial magnetic field by axial HF current (f=50 MHz) is investigated in the coaxial waveguide under the weak external axial field (⩽1.5 Oe). The gyrotropic sample-amorphous Co-based wire (15 μm in radius) serves as the central conductor of the wave-guide. Coefficient of energy transformation reaches magnitudes of the order of tens percent and is highly sensitive to external field due to the manifestation of the GMI-effect View full abstract»

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  • Performance of a d=0 Demod/Remod detector with partial erasure matching

    Page(s): 2803 - 2805
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    This paper describes the bit-error-rate (BER) performance of a Demod/Remod detector matched to a magnetic recording playback signal with partial erasure (PE) having d=0 run-length-limited (RLL) coded data. Previous work on Viterbi detection with PE is extended by the discovery of a 10-state detector and by generalizing the technique to an EPR4 partial-response target. A Demod/Remod detector is described which approximates the EPR4/PE detector with lower complexity. BER performance results are given for this detector on data taken from a commercially available magnetic disk drive View full abstract»

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  • High magnetic field sensitivity of TbFeCo layer and Pt/Co multilayers with an ultra-thin RE-rich RE-TM layer

    Page(s): 3229 - 3231
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    We studied the magnetic field sensitivity of double layer disks which were composed of a TbFeCo recording layer with low Tb content and a high-Tc RE-rich DyFeCo ultra-thin layer. The Tb14Fe82Co4/Dy30Fe35 Co35 double layer disk has better magnetic field sensitivity than a TbFeCo single recording layer disk. It was found that the film having such a large magnetization as Tb14Fe82 Co4 can be used for MO materials. Furthermore, we investigated the Pt/Co multilayers as a recording layer with an ultra-thin RE-TM layer. The addition of the ultra-thin RE-rich TbCo layer on the Pt/Co multilayers is effective for improvement of the C/N and the field sensitivity as well as that on the TbFeCo recording layer View full abstract»

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  • Timing acquisition for DFE detection

    Page(s): 2761 - 2763
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    A rapid and reliable acquisition procedure is proposed for DFE detection. This new approach eliminates the false-lock problem which arises in these detectors due to the decision feedback. The acquisition process comprises four distinct steps. It is illustrated with MDFE detection on the magnetic recording channel. Monte-Carlo simulations verify the robustness and accuracy of the acquisition process View full abstract»

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  • Time decay of magnetization in longitudinal CoCrTa/Cr high density thin film media

    Page(s): 3025 - 3027
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    A systematic experimental study of the time decay of the magnetization (M-decay) in longitudinal CoCrTa/Cr high density thin film media with different thicknesses at various levels of in situ reverse magnetic field which simulates the demagnetization field in recorded bits is presented. Two series of thin film media with the thickness of magnetic layer ranging from 90 Å to 1500 Å were deposited by RF/DC magnetron sputtering. The magnetic properties and M-decay were measured at room temperature using a vibrating sample magnetometer and an alternating gradient force magnetometer. The emphasis was placed on the M-decay at various film thickness. It is found that the coefficient of magnetic viscosity is not a constant over 5 decades decay time (sec.), the M-decay percentage exhibits a well pronounced peak at the reverse field value-of the remanent coercivity, and the mechanism of M-decay is apparently different in thin and thick film recording media. The mechanisms of affecting the magnetic viscosities of thermally-induced time decay are explored View full abstract»

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  • Thermal microscopy of spin-valve and magnetoresistive devices

    Page(s): 2923 - 2925
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    A thermal scanning microscope has been used to characterize the temperature of the different constituents of a thin film recording head under bias conditions. It shows that the temperature rise is highly concentrated in the current-biased read sensor. The results confirm calculations showing that most of the heat is dissipated through the shields, with the slider substrate acting as a heat sink. They also indicate that in SAL type AMR heads, the AMR layer is hotter than the SAL View full abstract»

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  • Index phase output characteristics of magnetic rotary encoder using a magneto-resistive element

    Page(s): 3370 - 3372
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    The purpose of this paper is to develop a magnetic rotary encoder with a resolution more than 4000 pulses per revolution in a magnetic drum with a diameter of 35 mm. The required resolution is more than 2000 pulses per revolution. As the resolution increases, ever greater accuracy is needed in the index phase to detect the original position of the encoder. To stabilize the index pulse, the authors took into account the width of the magneto-resistive element and the magnetization current wave form. As a result, the index pulse has been extremely steady in the magneto-resistive element with a width of 20 μm. It is pointed out that a pulse width of less than 6.9 μm is necessary for 4000 pulses per revolution. Moreover, the usable detection gap could be expanded by magnetizing the drum in a wave form in which both sides of a rectangular wave curved inward View full abstract»

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  • Flying characteristics of a slider over textured surface disks

    Page(s): 3196 - 3198
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    The effects of circumferentially ridged disk surfaces on a slider's flying characteristics are studied. Adding the circumferential ridges increases the trailing edge fly height and decreases the pitch because of the reductions in the effective flow area and restrictions in side-flows. The rates of of change of fly height and pitch increase rapidly as the disk velocity decreases. The ridged disk surfaces increase the air bearing damping ratios more in the vertical and roll directions than the pitch direction through the enhancement of the viscous shearing across the ridges View full abstract»

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  • Experimental performance comparison of FDTS/DF detectors: 8/9 (0,k) vs. 4/5 MTR codes

    Page(s): 2731 - 2733
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    The performance of an FDTS/DF detector is compared using two different RLL coding techniques. The new Maximum Transition Run (MTR) codes have been proposed for use with FDTS/DF detectors because of demonstrated coding gains. This work compares the performance of an 8/9 (0,4/4) code to a 4/5 MTR code using actual MR head signals captured from a spinstand. The coding gain is evaluated in the presence of real write process non-linearity that exists at high linear densities. The error rate performance is compared at User Bit Densities (UBD) ranging from 2.2 to 2.9. A technique similar to Sequenced Amplitude Margin is used to assess error rate performance for the FDTS/DF detector. Final results are also compared to PR4 and RAM-DFE detectors View full abstract»

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  • The effect of MR head nonlinearity on MDFE and PRML performance

    Page(s): 2764 - 2766
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    The detection performance of multi-level decision feedback equalization (MDFE) and partial response with maximum likelihood detection (PRML) in the presence of magnetoresistive (MR) head nonlinearity is investigated through simulation. Two models are used to characterize the MR head nonlinearity: (1) a transfer function curve based on measurement and (2) a 3rd-order polynomial model. The results indicate that MDFE is more robust to MR head nonlinearity than PRML, especially to head saturation View full abstract»

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  • Experimental study of thermal decay in high-density magnetic recording media

    Page(s): 3028 - 3030
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    The thermal decay of written bits in CoCrPt/CrTi thin film media for high density longitudinal magnetic recording is examined using a magnetoresistive head at room temperature. A decay in signal output over time is observed for the media with a thin magnetic layer less than about 14 nm thick and the media noise increases. The thermal stability factor Ku.V/k.T of these media is estimated to be less than about 100. The signal decay and noise increase are more serious at higher linear recording densities. These results are consistent with the results of a micromagnetic simulation taking into account the thermal aftereffects. These characteristics suggest that media with a large magnetic anisotropy constant Ku will be required to realize high storage densities of over 10 Gb/in2 View full abstract»

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  • High signal-to-noise ratio of a Cr-rich CoCrPt perpendicular medium with a large medium thickness

    Page(s): 3079 - 3081
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    A Cr-rich (Co72Cr28)94Pt6 perpendicular medium with a large thickness of 300 nm, integrated with an MR head designed for longitudinal recording, achieved a high signal-to-noise ratio of 37 dB at 100 kFCI and a D50 of 150 kFCI. A high Pt content of 17-22 at.% is effective for increasing the Hk value and signal amplitude at 10 kFCI, and for decreasing the write demagnetization. However, it also decreases the S/N at 100 kFCI and the D50. The signal amplitude rapidly increases with the Pt content from 0 to 6 at.%, and saturates at around 6 at.%. This contributes to the high S/N obtained at a Pt content of 6-11 at.%. Compared with a longitudinal medium optimized for the same MR head, the proposed medium has a 2 dB higher S/N at 100 kFCI, a 1.3 times larger D 50, and a 1.5 times larger signal amplitude at 10 kFCI. The thickness of the medium will contribute to the thermal stability of magnetic bits at future high recording density of 10 Gbits/in2 and beyond View full abstract»

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  • Characterization of the head-disk interface for proximity recording

    Page(s): 3112 - 3114
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    Lubricant additives and nitrogenated carbon overcoat are frequently used for the head-disk interface (HDI) of the proximity recording technology. The results show that lubricant degradation can be reduced by lubricant additives such as cyclic phosphazenes but excessive amount of the additive will accumulate on head and form marks on disk surface which is detrimental for the drive performance. Use of nitrogenated carbon for overcoat makes it possible for tailoring the HDI by increasing the overcoat conductivity and modifying the bonded lubricant thickness View full abstract»

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  • Optical metrology for MR heads

    Page(s): 2926 - 2928
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    The volume production of magnetoresistive heads requires fast and precise measurement of many critical material parameters such as film thickness and roughness. Optical metrology is ideally suited to perform these measurements. We review and demonstrate the application of Ellipsometry and Scatterometry for MR head metrology. We report results for NiFe film thickness measurements and Sendust surface roughness measurements with sub-Angstrom precision and repeatability View full abstract»

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  • Effects of CrNi pre-layer on magnetic properties of CoCrTa longitudinal media

    Page(s): 2974 - 2976
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    We have found that higher coercivity can be achieved on CoCrTa/Cr films by introducing a CrNi pre-layer between underlayer Cr and NiP plated layer. Coercivity is dependent on the Ni content in CrNi layer, and shows a maximum at Ni=40at%. Comparing crystallographic texture and microstructure of the media with and without Cr60Ni40 pre-layer, we concluded that the increase of coercivity is attributed to a reduced intergranular magnetic coupling View full abstract»

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  • The effects of underlayer NiFeX on the magnetic properties of CoPt films

    Page(s): 2908 - 2910
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    The effects of soft magnetic underlayer, NiFeX, on the magnetic properties of CoPt films has been studied as a function of substrate bias and Ar pressure during the NiFeX deposition and sputter etch time prior to the CoPt film deposition. It is concluded that the FCC (111) texture of NiFeX plays a dominant role in the c-axis orientation of CoPt films, Applying substrate bias or using P-Ta as an underlayer, the FCC (111) texture of NiFeX films can be greatly enhanced. Applying no substrate bias and sputtering at high Ar pressure, the FCC (111) texture of NiPeX films can be suppressed. As a consequence, the anisotropy of the CoPt films can be made either in-plane or perpendicular depending on the crystallinity of the NiPeX films. It is also found that a strong ferromagnetic exchange field between NiPeX and CoPt films favors the growth of CoPt films with c-axis in-plane, with a typical symptom of high in-plane moment thickness product and low remnant coercivity 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