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The granular hcp [Co.sub.3] Pt nano-grains with large perpendicular coercivity ([Hc.sub.[perpendicular to]]) of 3800 Oe and high perpendicular squareness ([S.sub.[perpendicular to]]) of 0.93 can be achieved by deposited 14 nm thickness of [Co.sub.3]Pt magnetic layer onto the Pt underlayer with thickness of 200 nm and annealing at low temperature of 300[degrees]C in a vacuum of 1 mTorr. It is found that the oxygen atoms would diffuse into [Co.sub.3]Pt layer through inter-grains to isolate [Co.sub.3] Pt grains and prevent grain growth that will decrease inter-grains interaction and enhance recording density of the magnetic film. This film revealed its prominent potential to be applied as perpendicular magnetic recording media for ultra high-density recording. Index Terms--Granular [Co.sub.3]Pt nano-grains, perpendicular coercivity, perpendicular magnetic recording media, perpendicular squareness.

It is necessary to develop a perpendicular magnetic recording head for the high magnetic field density of the recording region with small magnetic field leakage. This work suggests a topology design of the perpendicular magnetic recording head based on the density method. In order to determine the shape of a magnetic head with the return yoke, the topology optimization method is combined with the finite element method. Obtained results are also compared with results of the previous studies. Index Terms--Perpendicular magnetic recording system, recording head shape design, sensitivity analysis, topology optimization.

This paper proposes a new approach to magnetic recording based on shingled writing and two-dimensional readback and signal-processing. This approach continues the use of conventional granular media but proposes techniques such that a substantial fraction of one bit of information is stored on each grain. Theoretically, areal-densities of the order of 10 Terabits per square inch may be achievable. In this paper we examine the feasibility of this two-dimensional magnetic recording (TDMR) and identify the significant challenges that must be overcome to achieve this vision. Index Terms--Areal-density, capacity, granular media, magnetic recording, shingled writing, two-dimensional.

The core of the current granular perpendicular magnetic recording (PMR) media is the granular oxide magnetic layer (GOML). We observe that a fcc NiW seed layer, followed by a hcp Ru layer sputtered under low pressure (LP-Ru) and then by a hcp Ru layer sputtered under high pressure (HP-Ru) provides an excellent structural template for the granular oxide magnetic layer (GOML). Microstructure and magnetic properties of the GOML can be tailored through process conditions and alloy compositions to maximize the recording performance of the perpendicular magnetic recording media. Exchange coupled composite (ECC) media design provides significant improvement in overwrite (OW) and signal-to-noise ratio (So NR) for perpendicular magnetic recording media. Recording performance of the ECC media needs to be optimized with consideration of the magnetic properties and thicknesses of both the exchange control layer (ECL) and the cap magnetic layer (CML). At their respective optimum, the recording performance of the ECC media is mostly dependent upon the properties of the GOML and CML. This study indicates that a dual magnetic cap layer structure consisting of low-Ms and high-Ms sublayers can combine the benefits provided by the two types of cap magnetic materials. Index Terms--Dual magnetic cap layer, exchange control layer, exchange coupled composite media, granular oxide magnetic layer, perpendicular magnetic recording media.

This paper discusses the role of media damping for a perpendicular recording system that uses a realistic head field and media parameters in a micromagnetic model based on the Landau-Lifshitz-Gilbert formulation for the magnetization dynamics. The modeling approach uses pulsed write fields of varying pulse duration to record footprints of the head on the media. Using a criterion that 95% of the grains are reversed in the footprints, we calculate the field needed to record as a function of pulse duration, i.e., the dynamic coercivity. As shown in a previous paper, we find two distinct regions in the dynamic coercivity plots. The thermally dominated (long time) region can be described by appropriately including the demagnetization effects in the thermal stability factor [K.sub.u]V/[k.sub.B]T. The short time (dynamic) behavior shows a precipitous increase in the required recording field accompanied by an increase in the erase width. The latter effect causes the recording performance to degrade, especially in the short time dynamic regime. The onset of dynamic effects strongly depends on the media damping. In order to achieve high data and high areal density, we need to optimize damping in the recording heads and media. Index Terms--Damping, data rate, dynamic coercivity, Landau-Lifshitz-Gilbert equation, relaxation mechanism.

For present write channel current waveforms, a bandwidth efficiency of 1/2 bps/Hz is shown to be achievable which is 1/4 that of the read channel bandwidth efficiency. Further, with an improved write channel current waveform, the writer bandwidth requirement can be reduced by 1/2 to enable a bandwidth efficiency of 1 bps/Hz. Index Terms--Band limited signals, disk drives, integrated circuit interconnections, perpendicular magnetic recording, pulse analysis.

An alternative has been sought for the very hard ceramic material (Al20a plus TiC) used as the substrate for magnetic recording heads. We have substituted silicon as the substrate and slider body material; the primary insulator enclosing the recording head was made of Si[O.sub.2]. We built and tested these sliders with full read and write capability in disk drives. Si provides improvement with respect to hardness, modulus, and thermal conductivity, and adds the potential of active electronics located immediately adjacent to the recording head. We describe a novel means of producing heads, using entirely dry etching, rather than diamond sawing. The sliders were etched from the finished wafers in the form of individual sliders, rather than rows of sliders, and were processed individually through to completion. Conventional air bearings were etched into the sliders, suspensions were attached, and drives were built and tested. The outcome shows a profound advantage in the mechanical head/disk interaction, particularly under shock conditions. Other results and slider characterization are described. Index Terms--Disk drive shock resistance, magnetic recording, silicon slider.

Read heads using current-perpendicular-to-plane (CPP) giant magnetoresistance sensors have been fabricated and tested under highdensity recording conditions. A magnetoresistance of 5.5% and shield-to-shield spacing of 45 nm have been achieved by using an all-metal single-spin-valve with Heusler-alloy-based free and reference magnetic layers. Read heads with magnetic read widths ~45 nm were tested on perpendicular media, resulting in signals above 1 mV and signal-to-noise ratio ~30 dB. Linear densities in excess of 1050 kbpi were achieved with thermal fly-height control, compatible with recording areal densities of ~ 400 Gb/in (2). Current-induced spin-torque effects in the recording head were observed to result in rapid performance degradation above a threshold bias voltage of about 75 mV, corresponding to current densities > 10 (8) A/cm (2). Index Terms--CPP-GMR, magnetic recording, read-head, spin-valve.

We report on fabrication of discrete tracks on perpendicular magnetic recording (PMR) media with an e-beam lithographical process. We studied the recording performance of the e-beam media on a spinstand in parallel with conventional PMR media. Discrete track media show significant reduction in adjacent track erasure (ATE). We studied and quantitatively measured the source of the ATE improvement, and developed a triple track geometrical model to calculate achievable track density for both discrete track recording (DTR) and continuous media. From the model, we identify two factors of DTR that contribute to reaching a higher TPI. Using the same fabrication technique, we also studied servo burst design and its playback waveform quality. At 250 ktpi, we compare DTR servo bursts with servo bursts written with a conventional method. DTR servo bursts show better edge definition, which can translate to better position error signal sensitivity and support higher TPI in the future. Index Terms--Electron beam lithography, patterned media, perpendicular magnetic recording, servo.

We report a silicon area efficient method for designing a quasi-cyclic (QC) low-density parity-cheek (LDPC) code decoder. Our design method is geared to magnetic recording that demands high code rate and very high decoding throughput under stringent silicon cost constraints. The key to designing the decoder is to transform the conventional formulation of the min-sum decoding algorithm in such a way that we can readily develop a hardware architecture with several desirable features: 1) silicon area saving potential inherent in the min-sum algorithm for high-rate codes can be fully exploited; 2) the decoder circuit critical path may be greatly reduced; and 3) check node processing and variable node processing can operate concurrently. For the purpose of demonstration, we designed application specific integrated circuit decoders for four rate-8/9 regular-(4, 36) QC-LDPC codes that contain 512-byte, 1024-byte, 2048-byte, and 4096-byte user data per codeword, respectively. Synthesis results show that our design method can meet the beyond-2 Gb/s throughput requirement in future magnetic recording at minimal silicon area cost. Index Terms--Decoder, low-density parity-check (LDPC), min-sum algorithm, very large scale integration (VLSI).

With ever increasing a real density, interactions of particles with a head-disk interface become an ever more important factor impacting the drive reliability. Although particles trapped between the head and the disk could induce mechanical damage to the media resulting in permanent loss of data, data loss has also been observed without any obvious signs of physical damage to the media. We devised a component-level test to study this mode of data erasure on both glass and aluminium media. Our data indicate that the frictional heating associated with contact force between the particle and the disk could lead to permanent loss of data. In addition, we performed investigations to study the impact of air bearing design features, load/unload mechanism, and particle number density on the head disk interface. [DOI: 10.1115/1.2768071] Keywords: magnetic recording, particles, data erasure

In regards to servo-writing with perpendicular recording, we investigated servo-write quality and servo performance, and found that the premagnetization conditions, the magnetic-flux flow mechanism, and head structure strongly affect the servo-write quality. In response to these findings, we clarified that the flux flows through the writer to the reader are one of the root causes of servo-signal deterioration. In addition, we found that the flux amount is related to the magnetization switching ratio (MSR)--a one sided magnetization pole per writer-pole area. On the other hand, the reader can absorb flux even if it is far from the flux source. This means that not only the reader element but also the adjacent structure can absorb flux from the flux source. Index Terms--Magnetic flux, NRRO, perpendicular recording, RRO, self-servo-write, servo signal quality, servo-track-write.

Particle-induced damage on perpendicular recording media can be categorized as physical damage to the media and magnetic erasures with limited physical damage. Component-level tests were developed in order to measure particle robustness of air bearing designs for these two failure modes. A published model for air bearing interactions with a particle was extended to include the full slider surface and allow particles to slide along the slider air bearing features. The model and test results correlate for hard particle scratching. Specific air bearing features and properties can be modified in order to improve dramatically the air bearing particle robustness for hard particle scratches and particle-induced magnetic erasures. Index Terms--Air bearing design, magnetic erasures, particle-induced damage, particles.

Recent progress in the development of patterned magnetic recording media is presented, focusing on the results of patterned media fabricated by a self-assembled mask process. Several issues such as fabrication process, flyability, and signal processing have been discussed so far. However, recent progress seems to resolve these problems. A fabrication process using nano-imprint lithography is a possible solution in terms of productivity. Good results for flyability have been reported for discrete track recording media. Certain advantages with respect to signal processing have been reported. Although problems remain to be resolved, patterned media is expected to be commercialized following the introduction of the discrete track media, as a high density perpendicular magnetic recording media. Index Terms--Magnetic recording medium, nano-imprint lithography, patterned media.

The advent of iteratively decodable codes has allowed a decrease in tolerable signal-to-noise ratios (SNRs) in magnetic recording systems, which typically translates into an increase in the recording densities. However, at such low SNRs, conventional timing recovery loops suffer from frequent cycle slips. Typical timing recovery loops in magnetic recording applications perform data detection, timing error detection, and loop filtering in a sequential manner. This sequence of operations in the timing recovery loop performs well if the timing error is a small fraction of the bit interval. However, in the cycle-slip regions, the timing error is comparable to the bit interval, and the loop falls. In this paper, we represent the timing error in magnetic recording systems by using a Markov model that does not confine the timing error to only small fractions of the bit interval. By utilizing such a model, we give a trellis representation of the timing error process. The trellis representation permits the formulations of two optimal baud-rate timing recovery loops, according to two optimality criteria. We prove that both optimality criteria lead to solutions similar to the classical first-order phase-locked loop. The new loops do not perform data detection, timing error detection, and loop filtering in a sequential manner. Instead, the loops perform data detection and timing error detection jointly on a trellis, without the need for a loop filter. Simulation results show that the new timing recovery loops outperform the standard second-order baud-rate Mueller and Muller phase-locked loop with fine-tuned loop parameters. This performance gain is substantial if the timing error process is extremely noisy or if there is residual frequency offset resulting from inaccurate acquisition from the sector preamble on a disk drive. Index Terms--Intersymbol interference, phase-locked loop, timing recovery, trellis.

We have investigated an adaptive reliability-based iterative soft-decision Reed-Solomon decoding algorithm using belief propagation and we propose a reduced-complexity version of this algorithm. We discuss implementation and performance evaluation of these algorithms on magnetic recording channels. Index Terms--Belief propagation, iterative decoding, magnetic recording, reduced-complexity algorithms, Reed-Solomon codes, reliability-based decoding, soft-decision decoding.

By matching a singular function approximation to the Fourier solution at the air-bearing surface (ABS), we have derived a three-dimensional (3-D) analytic model of a shielded giant magnetoresistive (GMR) head, with side shields, for perpendicular replay. We present an explicit expression for the potential in the ABS and give values for the parameters in that expression for a range of practical head dimensions. Using only a few terms of this singular potential model, we show that the vertical field is accurate to within 1% of the sensor potential in the region of the medium for the majority of head dimensions suitable for magnetic recording. Index Terms--Distal recording, magnetic recording/reading heads, mathematics, perpendicular recording.

Acoustic emission (AE) transducers are commonly used to monitor the intensity of mechanical contacts in various sliding applications including magnetic head-disk interfaces (HDI). The authors introduce a method to obtain the electrical energy of the AE transducer from the output signal voltage. Calibration experiments were run to determine the calibration factor for converting the AE electrical energy to mechanical energy that is released during mechanical contacts at the HDI. Analytical models to calculate the energy released as a result of mechanical contacts arising from slider-disk interaction, from the presence of particulate contamination at the HDI, and those from head-disk interactions during dynamic load/unload (L/UL) in L/UL drives are presented. Experimental results for some of the cases described by the models are presented. Index Terms--Acoustic emission, head-disk contact, mechanical energy, tribology.

Dynamic characteristics of a tripad contact recording head over a random undulation disk surface are analyzed considering the surface energy of a thin liquid film lubricant. The head-suspension assembly is described in terms of a three-degrees-of-freedom (3-DOF) model. The configuration of the contact pad, the lubricant, and the disk surface is classified into four regimes, and the equations of motion for each regime considering the meniscus force and the contact force are solved. It is clarified from the simulation and multiple regression results that the surface energy has significant effects on the dynamics of the contact slider. Index Terms--Contact slider, three-degrees-of-freedom (3-DOF) model, meniscus force, surface energy.

Hard disk drive (HDD) servo technology for media-level servo track writing (MLSTW) is developed. MLSTW is the process of writing servo signals on magnetic disks before they are assembled in drives. It supplies a solution to achieve low-cost and accurate means of servo-signal writing. The HDD servo controller for MLSTW drives compensates for radial and rotational distortions of the servo signals (e.g., track-address, eccentricities, and servo-signal timing) that are inherent in the MLSTW method. The authors prove that the positioning accuracy is improved and the seek time is unchanged by using the new servo controller for HDDs with MLSTW disks. Index Terms--Calibration, delay effects, disk drives, distortion, feedforward systems, magnetic disk recording, position control, STW.

Novel fast seek and settling controls for hard disk drives (HDDs) have been developed. The controls are suitable for digital control and can be implemented into the servo program of a HDD's microcontroller easily. The controls use a feedback control and a feedforward control that uses feedforward trajectory with little power at actuator resonance frequencies. A finite-impulse-response notch filter is used to design the feed-forward trajectories. The seek control uses the pair of feedforward trajectories of position and current. The settling control that connects a long-distance seek control with a following control uses two pairs of feed-forward trajectories for initial position and initial velocity and a new bias-estimation method. The authors prove both controls are fast and free from residual vibrations and bias offset. Index Terms--Digital control, disk drives, feedforward systems, FIR digital filters, position control, resonance, state estimation, velocity control.

The authors investigate the flow structure in 3.5-in hard disk drives with a rotation speed of 10 033 rpm, especially the unsteady flow around actuator arms with and without a weight-saving hole, and clarify the unsteady flow in detail. In the method of approach utilized in this investigation, they used: 1) a direct numerical simulation of the Navier--Stokes equations to analyze the flow field; 2) a laser Doppler velocimeter to measure the velocity field; and 3) a laser Doppler vibrometer to monitor unsteady displacement of the actuator arm. The authors find a three-dimensional spiral vortex in the wake region of the arm and the flow spilled from the weight-saving hole. These flows can be considered to be an excitation source for the actuator arm. The power spectrum of the arm torque generated by calculated wind disturbance agrees with that of measured wind disturbance. This verifies the existence of the predicted vortices and the flow spilled from the weight-saving hole. Index Terms--Airflow, fluid analysis, hard disk drive, spiral vortex.

This paper describes design and fabrication of active head sliders using PZT thin films for in situ flying-height control. Silicon sliders with piezoelectric unimorph cantilevers were fabricated monolithically using micromachining process. The deflection of 70 nm was obtained at the tip of the 0.6-mm-long cantilever with a drive voltage of 4 V. Furthermore, an air-bearing surface design that makes it possible to reduce the aerodynamic lift force under the head is discussed. Index Terms--Hard disks, microactuators, microelecto-mechanical devices, piezoelectric films.

A phase-stabilized servo controller was developed based on a Nyquist plot for moving-suspension dual-stage actuators. The controller uses the suspension resonances of a PZT microactuator to compensate for the track misregistration (TMR) due to windage disturbance caused by suspension vibration. Experimental results obtained using a prototype 3.5-in hard disk drive show that the crossover frequency of the open loop is 2.0 kHz, and that the root mean square of the TMR due to windage disturbance is reduced by 23% compared to that of a conventional notch-based dual-stage controller. Index Terms--Decoupled feedback control, dual-stage actuator, hard disk drive, windage.

A computationally effective fixed-order multirate digital control scheme is presented for disk drive actuator control. The proposed multirate controller outputs control commands at each control update instant, while the multirate control scheme is evenly computed for every measurement sampling period, thereby eliminating the need for very powerful processors for implementation. Application results demonstrate that the proposed multirate control scheme is useful to smooth control inputs so as not to excite the flexible mode dynamics of the actuator arm and suspensions. Index Terms--Digital control, disk drives, multirate, resonance mode, Sampled data systems, stability.

An actuator consisting of a linear air bearing and a voice coil motor (VCM) of the linear type was designed for precise tracking. The stiffness of the air bearing was strong enough so that the moving coil of a VCM fixed to the air bearing slider arm could form a cantilever system. The linear actuator showed a much higher resonance frequency than a conventional rotary actuator. Due to the high resonance frequency, the servo bandwidth became significantly wider. The linear actuator could be stepped at 1-nm resolution without overshoots and undershoots and the rise time was less than 0.5 ms. Index Terms--Linear actuator, linear tracking, position control, precise positioning, servo writing, track following.

Unsteady airflow in an actual hard disk drive (HDD) which has a rotary actuator is numerically simulated by using the large eddy simulation technique, and the aerodynamic force affecting head gimbal assembly (HGA) is estimated from the simulation. The calculated force is fed to a structure analysis to predict the airflow-induced vibration of the HGA. The authors calculate the head positioning error or the head displacements for the different HGA orientations to explain and classify the mechanism of airflow-induced positioning error (i.e., windage) in HDD. Index Terms--Aerodynamics, CAE, displacement control, hard disk drive, numerical analysis.

This paper demonstrates an accurate mathematical model predicting forced vibration of rotating-shaft hard disk drive spindle motors with flexible stationary parts. The mathematical model consists of three parts: a rotating part, a stationary part, and bearings. The rotating part includes a flexible hub, a flexible shaft press-fit into the hub, and N elastic disks mounted on the hub. The stationary part can include motor bracket (stator), base casting, and a top cover. The bearings under consideration can be ball bearings or fluid-dynamic bearings (FDB). The rotating disks are modeled through the classical plate theory. The rotating part (except the disks) and the stationary part are modeled through finite-element analyses (FEA). With mode shapes and natural frequencies obtained from FEA, the kinetic and potential energies of the rotating and stationary parts are formulated and discretized to compensate for the gyroscopic effects from rotation. Finally, use of the Lagrange equation results in the equations of motion. To verify the mathematical model, frequency response functions are measured experimentally for an FDB spindle carrying two identical disks at motor and drive levels. Experimental measurements agree very well with theoretical predictions not only in resonance frequency but also in resonance amplitude. Index Terms--Fluid-dynamic bearing spindles, HDD spindle motors, vibration.

In the operation of fluid-dynamic-bearing (FDB) motors, the acoustic noise caused by the electromagnetic forces takes a big ratio in the noise level. The authors analyze the relationship between the acoustic noise frequency, harmonic current, and harmonic field, and propose a drive mode for reducing the acoustic noise of the FDB motors. The drive mode can also reduce the copper loss in the motor operation. Index Terms--Acoustic noise, drive mode, fluid dynamic bearing, spindle motor, torque ripple.

This paper presents the development of an ultraslim spindle motor for a 3.3-mm-height CF Type I disk drive. The mechanical structure of the developed motor is extremely miniaturized not only by eliminating the unnecessary space but also by optimizing the hub and clamp in order to fit in a small form factor. Electrically, it has the auxiliary winding in the linking part between the adjacent teeth of slotted stator, which increases the torque constant and efficiency. Simulation and experiment are performed to prove the advantages of the developed motor. Index Terms--Auxiliary winding, computer hard disk drive, high efficiency, high torque constant, spindle motor.

Ultrathin carbon nitride (C[N.sub.x]) overcoats were grown using pulsed dc magnetron sputtering. Substrates were mounted on a holder that allowed 45[degrees] tilt angle and rotation at different speeds. Effects of sputter gas composition, target power, substrate bias, substrate tilt, and rotation on film growth and properties were explored. Atomic force microscopy scans over large sampling areas show that thin C[N.sub.x] films obtained at--100 V substrate bias with 45[degrees] substrate tilt and 20 r/min rotation have root-mean-square roughness almost four times lower than those prepared without substrate tilt and rotation. Several percent of helium in an Ar-5%[N.sub.2] sputter gas was found to improve surface roughness of these coatings. These 1-nm-thick ultrasmooth coatings reduced corrosion damage compared with coatings of the same thickness grown without substrate tilt and rotation. This improved performance appears to be directly related to the growth of smoother and denser coatings synthesized under the present conditions. Index Terms--Coatings, corrosion, hard disks, sputtering.

Vibration analysis and experimental study of a disk-spindle system in hard disk drives are presented in this paper. The natural frequencies, mode shapes, and frequency response are calculated with the consideration of the flexibility of rotor and base structures of a disk-spindle system. The analytical model is verified by comparing the simulation results with the experimental data for a variety of motor configurations and sizes. It is shown that they agree very well with each other. Index Terms--Disk-spindle system, frequency response, mode shape, natural frequency.

An assessment of the chemical environment, within which a disk drive's head/disk interface must operate, is presented. This provides the framework for discussing the benefit of an internal, integrated chemical filter (ICF) to the long-term integrity of the head/disk interface. The ICF in the present embodiment has a diffusion limiting channel at the drive's breather inlet to minimize the rate of volatile contamination ingress, a mass of chemically treated, activated charcoal to permanently absorb acid gases and volatile organic compounds, and a particle filter to stop the ingress of external particles and charcoal fragments. The activated charcoal has the additional property of reversibly absorbing water vapor, which is used to moderate changes in the humidity within the drive. The design and performance of the ICF are discussed. Index Terms--Activated carbon or charcoal, chemical integration, contamination, corrosion, corrosive gas, disk drives, filter technology, humidity control.

In this paper, we present rigorous simulation tools: a lattice-based simple reactive sphere model, an off-lattice bead-spring Monte Carlo model, and a molecular dynamics model. These tools accurately describe the static and dynamic behaviors of perfluoropolyether films consistent with experimental findings (scanning microellipsometry and surface energy measurements). These are suitable for the description of the fundamental mechanisms of film dewetting and rupture due to instability arising from nanoscale temperature and pressure inhomogeneities. Index Terms--Air bearing, molecular dynamics, Monte Carlo simulation, perfluoropolyether (PFPE).

A novel visualization technique proposed by the authors was used to study slider-disk interactions during loading and unloading operations. The outcomes of the study prove that the visualization technique is a convenient, effective, and promising method for the investigation of slider-disk interactions. The performance of designed loading/unloading system can be evaluated effectively in a very short period of time. Many details, such as contact mode, type of contact, and so on, which have been invisible before, are now observable and have been revealed in this study. Index Terms--Head-disk interface, load/unload, magnetic recording, slider-disk interaction.

A new magnetic recording system is evaluated that includes the single-pole head, a new medium design, and the soft underlayer of perpendicular recording. The proposed medium consists of perpendicular grains with anisotropy directions tilted optimally about 45[degrees] with respect to the perpendicular direction. Here, focus is on the tilt angle at 45[degrees] in the crosstrack direction, including a small but typical dispersion. The write pole consists of a tapered-neck single-pole head with a very small throat height that yields maximized write fields without increased edge track degradation. The advantages of tilted perpendicular recording are discussed using theoretical and numerical micromagnetic analyses. This design achieves a much higher signal-to-noise ratio (SNR) than conventional recording, because it is less sensitive to medium orientation distributions and, for the same thermal decay, can utilize media with much smaller grain sizes. The switching speed is much more rapid due to increased recording torque. Estimated recording limits for tilted perpendicular recording with a medium-jitter SNR of 17 dB are beyond densities of 1 Tb/[in.sup.2] and data rates of 1 Gb/s. Index Terms--Data rate, micromagnetic simulation, perpendicular recording, recording method, signal-to-noise ratio, thermal stability, tilted perpendicular recording, track edge effect, transition parameter.

In this work, we present the general head design and magnetic recording performance of our second-generation advanced probe heads. These heads require as low as 5-mAo-p write currents for optimal recording. We demonstrate superior writeability via a series of overwrite (OW) and nonlinear transition shift (NLTS) saturation measurements. Excellent OW can be obtained with both high and low OW ratios. Media with VSM coercivities as high as 5500 Oe can be recorded with OW of 32 dB. We measured better than -12 dB of NITS at a linear density of 1500 kfci. In this work, we present data where the magnetic read width (MRW) for the same read head is smaller when measured on perpendicular media compared to longitudinal media. We also show that the external field sensitivity of the advanced probe heads is excellent as larger than 32 and 23 Oe of external fields are required to erase a low-density signal on 3380- and 2200-0e disks, respectively. Overall, the basic architecture of this advanced probe head is extendable to 0.12-[micro]m write track-width, while we discover no remanence in the pole. Index Terms--Finite-element model (FEM), head design, high areal density magnetic recording, perpendicular recording.

We investigated the fabrication processes used for single-pole-type heads for perpendicular recording. To solve the problem of side write/erase on adjacent tracks, it is necessary to develop a trapezoidal main pole for single-pole-type heads. We therefore proposed two different fabrication processes: 1) a process using electroplating and ion milling and 2) a damascene process using reactive ion etching and chemical mechanical polishing. We made the trapezoidal main pole using the damascene process. An evaluation showed that using a single-pole-type heads with a trapezoidal main pole solved the side write/erase problem. There was also no problem with the writing performance of the heads. To make a narrower track (less than 250-nm wide), we optimized the process conditions. Index Terms--Magnetic heads, perpendicular recording, single-pod-type-heads, trapezoidal.

A real density growth has enabled hard disk drives to continually fulfill the demands from new enterprise, desktop, and consumer applications. The demonstration of 100 Gb/[in.sup.2] is another milestone that was achieved recently and is described in this paper. The recording demonstration employed fully integrated magnetic recording heads and thermally stable multilayer antiferromagnetically coupled (AFC) media through a commercially available channel chip. At a track density of 149 ktpi and linear density of 680 kbpi, the achieved off-track capability with 5% track squeeze was 10% of the track pitch, while maintaining a raw bit-error rate (BER) of [10.sup.-4] or better. This yielded an areal density of 101 Gb/[in.sup.2] with measured on-track raw BER of 5 x [10.sup.-5]. Index Terms--Disk drives, magnetic heads, magnetic recording, system analysis and design.

The 'take-off' behavior of proximity recording sliders is investigated using acoustic emission and phase demodulated laser interferometry. A biquadratic surface fit of the air bearing surface is used to determine the position of the slider with respect to the disk. Acoustic emission data is examined in both the time and frequency domain to analyze the location of slider/disk contacts. Two distinct frequencies are observed in the frequency spectrum of the acoustic emission signal, corresponding to torsional mode and bending mode vibrations of the rigid slider. As the velocity increases, the magnitude of the torsional mode decreases relative to that of the bending mode, indicating that slider/disk contacts change from side rails contacts to trailing edge contacts.

A novel adaptive continuous-time forward equalizer (CTFE) for use with a decision-feedback equalizer (DFE) in the magnetic-recording read channel is presented. The forward equalizer is composed of one adaptive zero and can be constructed by adding a weighted version of the read-signal derivative to the read signal itself. The new equalizer is a viable alternative to traditional finite-impulse-response (FIR) forward equalizers in both performance and complexity. Index Terms - Adaptive equalizer, CMOS integrated circuits, decision feedback equalizer, intersymbol interference, mixed analog-digital integrated circuits.

In this paper, a modified equalization target is proposed for the high density magnetic recording channel. This target is a closer match to the channel than the EEPR4 response and hence has better detection performance. based on the dominant error events for this target, a parity-based coding scheme is also proposed to achieve a coding gain with the modified target. The use of the parity code detects the occurrence of the dominant error events while achieving a high code rate. The detection system consists of a Viterbi detector matched to the channel response and a post processor to handle the code constraints. This system is shown to perform well compared to other proposed detection systems through analysis and simulation on a Lorentzian based channel model. Index Terms - Digital magnetic recording, equalizers, modulation coding, partial response signaling, trellis codes, Viterbi decoding.

In this work, we study an EPR-IV system for high density digital recording and compare it to the PRML recording system. A combinatorial optimization technique that uses the simulated annealing algorithm in conjunction with a descent method is employed for optimization of partial response (PR) equalizers. The gradient algorithm to track variations of timing phase for the EPR-IV channel is investigated. Also, a generalized Viterbi algorithm is used for detecting the EPR-IV system. Simulation results demonstrate that at high recording density, a coding gain over the PRML system can be obtained for the EPR-IV system with a comparable complexity. Index Terms - Generalized Viterbi algorithm, partial response maximum likelihood (PRML) channel, simulated annealing, timing recovery.

A new equalization target for the high-density magnetic recording channel is proposed based on the PR1 partial response combined with decision feedback. A detector for the new target is developed and shown to allow practical implementation. The performance of the detector is assessed through analysis and simulation. It is shown that the detector is suitable for channel recording densities of 3 bits per [PW.sub.50]. Index Terms - Decision feedback equalizers, digital magnetic recording, local feedback, partial response signaling, Viterbi detection.

The magnetic properties of CoCrPt is discussed relative to sputtering power dependence. Several x-ray experimental methods were used for structural analysis.Correltation between strucural poper

This paper describes the design, fabrication, position sensing, and control of an electrostatically-driven microactuator. The polysilicon microactuator, together with an on-chip electronic buffer, were fabricated by the Modular Integration of CMOS and microStructure (MICS) technology. The microactuator has a linear dimension of 310[[micro]meter x 340[[micro]meter] x 1.7[[micro]meter] and a 'long throw' range of motion of [+ or -]4[[micro]meter]. The driving comb fingers of the microactuator can generate up to 0.3[micro]N of electrostatic force, which is able to pull the suspended microactuator across the substrate at an acceleration of over 270 G's. The lateral position of the microactuator, relative to the substrate, is capacitively sensed by a Kalman filtering scheme, which achieves a position estimation error covariance below 0.01 [[micro]meter] RMS. A state-variable feedback loop operates at a closed loop bandwidth of over 11 kHz. Experimental results are given.

It may seem surprising to find a Flash technology discussion at a conference on magnetics. Bulk data storage is the point of commonality for these two technologies. Computers commonly use magnetic disks to provide bulk storage of data. Flash memory technology appears to offer even better functionality in certain areas of this application. We will begin with an examination of the flash storage cell and how it works. From this we will be able to see the characteristics of flash and how they compare to the mass data storage requirements of portable computing.

To achieve a higher storage density on the overwritable exchange-coupled quadrilayer MO disk, the overwrite recording characteristics using the optical head with 680nm laser diode were investigated. High recording sensitivity was obtained and the write power was estimated to be about 10mW at 22m/sec linear velocity. CNR of more than 46 dB was obtained at 0.66 micrometer mark length, and 0.5 micrometer/bit recording with a bit error rate less than 1 X 10 to the -5 was succeeded at 1.2 micrometer track pitch. We have concluded that 130mm double-sided direct overwrite MO disk could have 2.5GByte storage capacity. If 1.0 micrometer track pitch disk can be used, a storage capacity of 3.5GByte might be expected.