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In this article, we discuss the models of the 747 test, in particular, the 747 test taken over a range of linear densities. In a comparison study, we fit the 747 curves at three conditions, as well as different upper limits of the track pitch. Based on the comparison result, we present a general model for the 747 curves as a function of linear density. The new proposed model not only improves the accuracy but also extends the applicable scope of the fitting. With the model, we also demonstrate the optimal combinations of track density and linear density for maximizing the off-track-capability (OTC) and squeeze-to-death (S2D), as well as their maximums as a function of areal density.

Some aspects of the challenges to high track density heat-assisted magnetic recording (HAMR) are addressed with a focus on track interferences (adjacent as well as non-nearest neighbor erasure). Comparisons with corresponding conventional perpendicular magnetic recording (PMR) parameters are also made. Adjacent and non-nearest neighbor track erasure data from functional HAMR and PMR drives and simulation data of signal-to-noise ratio loss in HAMR are also presented.

In order to ensure flight safety and eliminate hidden dangers, it is very important to detect aircraft track anomalies, which include track deviations and track outliers. Many existing track anomaly detection methods cannot make full use of multidimensional information of the relevant track. Based on this problem, an aircraft track anomaly detection method based on the combination of the Multidimensional Outlier Descriptor (MOD) and the Bi-directional Long-Short Time Memory network (Bi-LSTM) is proposed in this paper. Firstly, track deviation detection is transformed into the track density classification problem, and then a multidimensional outlier descriptor is designed to detect track deviation. Secondly, track outliers detection is transformed into a prediction problem, and then a Bi-LSTM model is designed to detect track outliers. Experimental results based on real aircraft track data indicate that the accuracy of the proposed method is 96% and the recall rate is 97.36%. It can detect both track deviation and track outliers effectively.

Dual stage actuators have recently been implemented in hard disk drive suspensions in order to increase the track density of hard disk drives. This paper investigates the lateral deflection (lateral stroke), stress distribution and design characteristics of a suspension-based and a collocated flexure-based dual stage actuated suspension design using finite element analysis. Design parameters for each suspension design are examined and guidelines for improved lateral deflection characteristics are proposed.

Achieving higher track densities in tape storage systems requires significant improvements in the track-following capabilities. The track-follow control system is used to reduce the misalignment between the tape and the recording head created by the lateral motion of the flexible medium. The characteristics of the lateral tape motion disturbance and their effect in the track-follow performance are identified. The effects from roller run-outs, reel eccentricities and tape paths with flangeless rollers are discussed. Control schemes are evaluated to improve the track-following capability and increase the track density on a magnetic tape.

Statistical investigations into off-track errors for shingled and conventional writing were carried out to reveal error behavior at high track densities. The residual data width in shingled writing tended to be wider than that in conventional writing for the same average track pitch. A comparison of the distributions of the calculated residual data width revealed that for conventional writing erroneous tracks were generated when the track was squeezed by both neighboring tracks, i.e., double squeezing. Shingled writing has an advantage in that this double squeezing does not occur and therefore a higher track density can be achieved.

Areal density capability of a recording system is traditionally determined in two steps. Linear density is first determined by on-track error rate. Track density is then determined by off-track read capability (OTRC) at the linear density chosen in step one (IEEE Transactions on Magnetics, vol. MAG-26, no. 5, pp. 1689-1693, Sep. 1990). With advances in technologies and changes in drive requirements, this traditional method does not necessarily reflect the current requirements and limitations of high density recording. In this paper, a new method to experimentally determine areal density capability is proposed. The limiting factors and demands to recording components will also be discussed.

We developed a new magnetic test to characterize the track overlapping effect in shingled magnetic recording. Media noise power and media noise track profile as a function of track trimming are directly measured on a spinstand tester. Pseudo-jitter and on-track noise depth are introduced as new recording parameters. Their effects on shingled track density are discussed.

A systematic experimental study of reverse overwrite (ReOVW) process in the shingled recording scheme has been conducted in conjunction with characterization of corresponding recording performances from recording heads with different geometries. It was found that not only is there no ReOVW reduction as the track density increases, but also ReOVW is, in fact, slightly increased from 300 ktpi to 600 kpi or beyond by using the same writing conditions. These data suggest that conventional magnetic recording technology might be able to extend all the way beyond an areal density of one Tbit/in2 by using the shingled recording scheme.

This paper addresses the effect of a shield for the ring head to improve high track density. We analyzed the shape and the position of the shield with the finite-element method and checked the effect of the shield using a three-dimensional magnetic recording simulator in which a curing magnetic reversal model and self-consistent magnetic calculations were combined with the finite-element method. In this analysis, all components of the fringing field of the shield head were reduced, especially for the 30-degree components, which refers to the orientation angle of obliquely oriented metal evaporated tapes. We calculated the side erase band (SEB) from recorded magnetization on DC erased obliquely oriented metal evaporated tapes and found an optimal shield shape and position with respect to the head/media spacing. The well designed shield head was advantageous in having an SEB that was less than half that of a conventional head, was effective for achieving high track density in a tape storage system.

We have compared track density capabilities of discrete track media and continuous perpendicular media by using a numerical model of off-track capability. In the model, off-track capability is obtained from the signal-to-noise ratio (SNR) cross-track profile. We have investigated the effects of read width, erase bandwidth, write width, and on-track media SNR. Our simulations show that the track density for discrete track media can be 25%-35% higher than that for continuous media. Track density advantage of discrete track media is reduced when the erase band width becomes wider or the on-track media SNR is higher.

In this paper, the feasibility of two-dimensional magnetic recording is discussed from the viewpoint of high track density. 747 curves of shingled track were measured using existing heads and media and were interpreted with a squeezing model dominated by the SN ratio of the read head output. As long as a reader can be placed on the median line of the squeezed data area, wider OTC than that of conventional writing will result. The modeled 747 curves were in good agreement with the experimental data for both conventional writing and shingled writing. The feasibility of narrow track pitch shingled writing was shown, however, write-to-write misregistration should be minimized to maximize the track density.

This research investigates how the design variables of ball bearing affect the bearing stiffness and the natural frequencies of a hard disk drive (HDD) spindle system at elevated temperature. It shows that any design change that increases the contact angle of ball bearing reduces the variation in the bearing stiffness and the natural frequencies at elevated temperature. This research also proposes a robust HDD spindle motor in which a wave spring maintains a constant preload minimizing the effect of temperature variation. Experimental modal testing shows that the reduction of the natural frequencies at elevated temperature is much less in the proposed HDD spindle system than in the conventional spindle system. The proposed HDD spindle motor can improve the dynamic reliability of a HDD spindle system, which contributes to the high track density of a HDD.

The discrete track technology is promising as the technology that makes high track density. It decreases cross talk from the adjacent track because the track is separated in physically and magnetically by the grooves. However, the magnetic head does not fly stably on the disk with grooves. Therefore, it’s necessary to make smooth surface by refilling the grooves with non-magnetic material. We tried to flatten the discrete track media surface by using the bias sputtering method and the etching back method in dry process.

A 0.6 /spl mu/m BiCMOS interface for microelectromechanical systems (MEMS) based rotational accelerometers is presented. It is housed in an inexpensive standard SO-24 plastic package with a capacitive rotational accelerometer sensor produced using MEMS technology. This sensitive interface chip includes the analog-to-digital conversion, filtering, and interface functions. The analog-to-digital conversion is realized through a single-bit electromechanical /spl Sigma/-/spl Delta/ loop able to detect capacitive unbalancing as low as 50 aF (50/spl times/10/sup -18/ F). The produced bitstream is then processed by a digital chain and made available through a standard 3.3 V (5 V tolerant) three-wire serial bus. The signal bandwidth is about 800 Hz, the sensitivity is 2.5 rad/s/sup 2/, with a full-scale sinewave of 200 rad/s/sup 2/ and a signal-to-noise ratio peak of 38 dB over 30-800 Hz. Through the serial bus, it is also possible to program device characteristics including gain, offset, filter performance, and phase delay. The complete sensor is used in a feed-forward compensation scheme to cancel external disturbances acting on computer hard-disk drives so as to steadily keep the read-write heads on track: this allows greater track densities and better speed performance.

In conventional hard disk drive signal recording, the track pitch and the track density depend mainly on the write/read width of the magnetic head. In order to increase the track density, a narrow head is needed. We are developing a discrete track media with perpendicular anisotropy to evaluate the capability of high recording density. The tracks are separated physically by the groove. Then, the recording width and the track pitch are defined precisely by the tracks formed on the media. It is expected to have some features for high track density recording. The recording track fluctuation during the writing process and the magnetic interference from adjacent tracks are reduced. Also, the recording signal at the write-pole-edge is improved, and so on. We fabricated an actual discrete track perpendicular medium to evaluate the basic write/read properties. The measurements have been carried out on a spin-stand. The capability of this media at high track density are discussed.

As track density increases, higher control bandwidth is required to attain sufficient positioning accuracy while suppressing the effect of high frequency disturbances in disk drive controllers/actuators. This paper presents a computation effective fixed order multirate digital control system. The multirate controller outputs control at each control update instant, while the multirate control scheme is evenly computed every measurement sampling period, thereby eliminating the need for very powerful processors for implementation. As the input multiplicity increases, the control command becomes smoother, without losing phase and gain margins, so as to reduce the chance of the actuator flexible mode excitation that should be avoided in high track density disk drive servos. Application results demonstrate how the proposed multirate digital scheme substantially removes the excitation of the actuator arm/suspension flexible mode dynamics due to the discrete stepwise control input.

This paper presents a design method of robust controller using the modified dual feedback controller to improve transient response in track seeking while attaining robust performance and stability in the presence of plant uncertainties. Coupled dynamics model is identified from the Newton–Euler formulation. We use discrete-time LQG/LTR controller design method. Robustness analysis is performed using the μ-analysis method. With the proposed method we are able to obtain an improved transient response. Furthermore, we can achieve the desired sensitivity functions while assuring robustness to the parameter variations to known structured uncertainties. It is demonstrated that the proposed method can be extented to short track-seek control without change of the controller structure. From simulation and experiment results, we confirm the effectiveness of the proposed method.

In this paper, disturbances, the source of TMR being the barrier to high track density of HDD are analyzed quantitatively using PES only without extra sensors. Disturbances are separated into RRO and NRRO, then, NRRO is separated into input torque disturbance, output disturbance, and noise. The effect of each disturbance on PES is compared. It is shown that PES NRRO measured in open-loop and in closed-loop can be used to calculate sensitivity transfer function. Using separated disturbances, PSD of PES RRO and NRRO are predicted for various gain levels in track following servo, and they are compared with PSD of PES measured in experiments. We propose that this can be used to predict servo performance accurately. Also addressed are some discussions on the differences between this work and the former contributing work.

Laser-assisted magnetic recording is an interesting method for narrowing a track pitch; in particular, crosstalk canceling in laser-assisted magnetic readout has a unique feature that it enables us to reproduce a narrower track than an assisting laser spot size. Shorter wavelength of the assisting laser promises the higher track density, accordingly. In this paper, we have demonstrated the crosstalk evaluation by using a blue laser for the assisting beam and obtained as high track density as 85ktpi.

A technique for reducing cross-recording on data storage media with high track density is described. In order to detect cross-recording sensitively, an inverted mark pattern was first recorded on adjacent tracks and then synchronized with a normal recorded mark pattern on the central track. These patterns were repeatedly recorded as the recording power was increased. Readout signals of the recorded mark pattern were evaluated on the central track in each condition, and an optimum recording power was precisely determined from the maximum amplitude of the signals. When this new technique was applied to a magneto-optical disk, the bit error rate was reduced to less than 10/sup -4/. This is the first technique to reduce cross-recording by laser power only.

The effect of magnetic pole shape on the remanent magnetization state at the track edge was studied for a ring-type head and a single-layered perpendicular medium system. An MIG head and a merged MR head were used for recording. These heads have symmetric and asymmetric magnetic pole structures, respectively. It was found that the remanent magnetization state at the track edge of a single-layered perpendicular medium was greatly influenced by the shapes of the magnetic poles. Thus it is necessary to improve the shape of magnetic poles in order to realize the higher track density for a single-layered perpendicular medium.

The HDD demands higher areal density for large capacity. However, in higher track density, the cross-talk issue at reading process and the side-write issue at writing process become critical. Discrete track medium, which has phiysically separated tracks and grooves, is expected as the most promising technology for improving these problems [1], [2], [3]. Track mis-registration of a magnetic head is generated during the read and write process. Therefore off-track-capability (OTC) is very important for achieving a HDD with higher track density. In this paper, the OTC of a discrete track medium and a conventional medium, which has continuous recording layer, are compared by using Landau-Lifshits-Gilbert micromagnetic simulation [4].

This paper reports results of experimental investigations on the relationship between skew angle and achievable recording density. Work is focused on bit density, track density and error rate aspects. The obtained results indicate that large skew angle reduces achievable bit density of both near-isotropic and orientated media. Increased skew angle also increases bit-shift value, therefore reducing applicable recording density from a reliability viewpoint. However, increased skew angle can support higher track density, as the effective track width and the writing interference are reduced when the skew angle is large. For certain head-disk integration, the width of the erase profile can reduce at a faster rate compared with the width of the track profile.

The phenomenal growth rate in track densities for magnetic hard disk drive systems poses significant challenges to the actuator control system. This paper investigates the problems that will be faced by the control engineer in pursuit of track densities that are significantly higher than available in existing disk drive products. Conditions on position sensing noise, control bandwidths and actuator resonances are projected in order to achieve the desired track densities.

A fluid-film spindle for 2.5 inch hard disk drive is described that effectively reduces nonrepeatable runout to less than 0.05 /spl mu/m, making it possible to increase track density. The spindle is used with a newly designed three-lobe bearing of which each lobe is asymmetrical. The influence of stiffness and temperature in a prototype spindle using this bearing are discussed and comparisons are made with a conventional ball-bearing spindle.

Successful use of a NiFe/Co/sub 90/Fe/sub 10/ bilayer as a soft magnetic free layer in spin-valve films with a GMR enhanced structure comprised of NiFe/Co/sub 90/Fe/sub 10//Cu/Co/sub 90/Fe/sub 10//FeMn is outlined. The GMR ratio of the spin-valve film with Co/sub 90/Fe/sub 10/ is over 7% and the coercivity of the free NiFe/Co/sub 90/Fe/sub 10/ bilayers is less than 5 Oe. A merged inductive/spin-valve head was fabricated with a read track-width of 1.3 /spl mu/m and a read gap-length of 0.26 /spl mu/m using spin-valve film with a Ta(50 /spl Aring/)/NiFe(45 /spl Aring/)/Co/sub 90/Fe/sub 10/(30 /spl Aring/)/Cu(32 /spl Aring/)/Fe/sub 10/(22 /spl Aring/)/FeMn(100 /spl Aring/)/Ta(100 /spl Aring/) structure and 260 /spl Aring/ thick domain control Co/sub 78/Cr/sub 10/Pt/sub 12/ magnet layers. Its read/write performance was tested on a low noise CoCr/sub 17/Pt/sub 5/Ta/sub 4/ thin film disk with an Mr/spl middot/t of 0.41 memu/cm/sup 2/ and a coercivity of 2500 Oe. There is no Barkhausen noise in the readback waveform. The result of the microtrack sensitivity profiles reveals an effective read track-width of 0.8 /spl mu/m. A normalized output for a track-width of 880 /spl mu/Vpp//spl mu/m and D/sub 50/ of 166 kFCI was obtained. Using a PRML channel, a bit error rate of less than 10/sup -8/ was obtained without error correction at a data rate of 3.3 MB/s and at a linear density of 217 kBPI on a thin film disk with an Mr/spl middot/t of 0.72 memu/cm/sup 2/. Thus, 5 Gbit/in/sup 2/ density recording with a linear density of 217 kBPI and a track density of 23 kTPI is possible.

High track density has been achieved by adopting an H∞ controller with a feed-forward compensator using adaptive filter theory in a sector servo system. In applying the H∞ control theory, a state-space model of an augmented plant was constructed considering the input location of the disturbance. Moreover, to reduce repeatable runout, an experiment involving a feed-forward control system including an adaptive FIR filter was performed. As a result, the head-positioning accuracy was improved by approximately 15 percent compared to the case without feed forward. A 0.15-μm head-positioning accuracy was achieved. This level of accuracy means that a track density of 310 tracks/mm (8100 TPI) can be realized.

Summary form only given. With the continued pressure on both the cost and capacity of archival storage requirements, current flexible media roadmaps now anticipate cartridge capacities in excess of 1 TB in the very near future. The increase in cartridge capacity can be achieved by increasing the linear data density and also the number of tracks written across the width of the tape. The planned increase in track density will require the recording head to write, and read, significantly narrower track widths than used in current flexible media products. Thus, as the track widths are decreased the width of the erase bands will become an increasing proportion of the overall effective written track width. It is therefore essential that both the erase band and effective write widths are fully characterized. We report here the results of extensive investigations of the influence of the write head design and operating point on both the effective write width and erase band width. The effective erase band widths in both directions were found to be very strong functions of the write current for the media used in these tests, while the write width depended both on which pole the track was written with and write current. The relative dimension of the inverted pole also played an important role in determining the write width.

There is a drive toward achieving much higher track density in magnetic recording. Increase in track density will produce more interaction/crosstalk between adjacent tracks. The simulated variation of bit error rate (BER) as a result of increased inter-track interference (ITI) using a Viterbi Detector is presented in this paper. Results show that for a given BER and signal-to-noise ratio (SNR), different levels of ITI can be tolerated depending on the code. Calculations suggest 2-dimensional modulation codes designed for a channel experiencing ITI can result in up to 23% gain in areal density.

Laser-assisted magnetic recording technology enables narrower track recording and reproducing than the track width of a magnetic head. The size of the assisting beam is a critical issue for high track density in this technology. In this study, the possibility of the 100 kTPI recording was demonstrated with laser-assisted magnetic recording using a blue laser.

Developments of magnetic head, recording medium, positioning, and signal processing technologies made it possible to perform magnetic recording at an areal density of 2 Gb/in/sup 2/ on a prototype 3.5-in diameter hard disk drive. A track density of 17 kTPI, which is comparable to or even greater than that used in optical storage systems, is used to minimize the reduction in the physical clearance between the medium and the head. The authors outline the system and its component technologies. The read/write characteristics of the 3.5-in prototype disk system are also reported. >

We deposited spin-valve films with a CoFeB/Ru/CoFeB synthetic ferrimagnet pinned trilayer and a PdPtMn anti-ferromagnet layer and investigated their MR responses. We also fabricated spin-valve heads having a Ta(50 /spl Aring/)/NiFe(20 /spl Aring/)/CoFeB(15 /spl Aring/)/Cu(30 /spl Aring/)/CoFeB(25 /spl Aring/)/Ru(8 /spl Aring/)/ CoFeB(15 /spl Aring/)/PdPtMn(150 /spl Aring/)/Ta(60 /spl Aring/) synthetic ferrimagnet spin-valve film. We tested the read/write performance on a low noise CoCrPt-based quaternary alloy thin-film disk. A narrow, effective read track-width of less than 0.4 /spl mu/m was measured. We obtained a normalized output with respect to track-width of 2500 /spl mu/Vpp//spl mu/m. Using a EPR4ML channel with a 16/17 code and an inductive head with a track-width of 0.45 /spl mu/m, we found a bit error rate to be less than 3.45/spl times/10/sup -6/ without error correction at a data rate of 13.3 MB/s and at a linear density of 405 kBPI on the similar disk. Furthermore, from squeeze measurements, we found the track-pitch to be 0.505 /spl mu/m, which corresponds to a track density of 50.3 kTPI. As a result, we accomplished an areal density of 20.4 Gbit/in/sup 2/ with a linear density of 405 kBPI and a track density of 50.3 kTPI using PdPtMn/CoFeB synthetic ferrimagnet spin-valve heads.

Side-fringing is an important factor for high track density recording. Track width written with a flying single pole flying head was measured through off-track profiles. The results show almost no side-fringing. The erase band width was around 25 nm for the off-track overwrite profile.

Successful error rate performance has been obtained at an areal density of 5 Gb/in/sup 2/ using dual element (thin film inductive write/AMR read) heads and low noise, high resolution thin film media with a PRML channel operating at 10 MB/s. A detailed investigation of the TMR requirements to achieve these densities is reported here. This analysis allows the trade-offs between linear density and track density, wide/narrow write and read heads, and TMR to be explored in a single context. Clear differences in TMR requirements exist between the three head designs in this study even though all are capable of 5 Gb/in/sup 2/. The best head design requires a TMR of

Recently, ultra high track density positioning methods have been studied as key technology to increase the capacity of disk drives. This paper introduces a new method, Graphic Head Positioning method (GHP), and compares it with other methods.

ABS-patterning is a known method for achieving the ever-increasing track density requirements of today's disk drives. This patterning leaves a shoulder on either side of the head which can affect the track profile of the head. Therefore, the height and width of this shoulder are important parameters to control when fabricating heads in this fashion. In this study, we examine the effect of the shoulder width and the shoulder height on the cross-track performance. We conclude that a shoulder height of 0.75 /spl mu/m is sufficient to minimize the effect of a shoulder width of up to 1 /spl mu/m. A 3D model was constructed and shows good agreement with the data. The model was used to predict throat-height tolerance and to model wider shoulder widths.

Three dimensional fringing fields of the writing part of the merged magnetoresistive heads with a flat and a partially trimmed shared pole have been computed numerically. Partial trimming of the shared pole considerably improves the track density of the MR head by means of reduction of a side write and a side erase bands. The influence of the shared pole geometry and pole material on recording performance of the merged MR head has been discussed.

A matrix thin film writing head and a magneto-optic readout system have been developed. They can write and read simultaneously more than 1000 parallel longitudinal tracks on a tape with high areal bit density. Such longitudinal recording systems are usually limited in track density by the intertrack interference and guiding errors in the tape transport. A simple transversal filtering over the tracks to remove intertrack interference and the behavior of a very simple and efficient optical track following servomechanism are presented. Both exploit correlations between tracks. Each track is identified by its own mean value that has been fixed at coding.

The calculation of soft error rate from models of the disk, head, and channel is used to predict optimum read and write widths for MR heads. For a 4.3 /spl mu/m track pitch, 120 kfci, and PR4 coding, the best write width is 3.8 /spl mu/m and the best read width is 2.9 /spl mu/m. The optimum write width is relatively insensitive to track misregistration and read and write width process variations. The optimum read width decreases with increasing track misregistration. The soft error rate is most sensitive to write-to-write track misregistration.

New inter-track orthogonal coding for high track density and multi-track recording is proposed. Two data code sequences are modulated by 2nd order Hadamard matrix elements so that they are orthogonal each other. The coding method exhibits an absolutely high rejection efficiency against cross talk noise from adjacent tracks, indicating feasibility not only of high track density recording but of collective reading of multi-track channel signals. It is expected from simulation results that an ultra high track density recording with neither guard-band nor azimuth between adjacent tracks would be possible for all kinds of information recording using sequential tracking.

To achieve higher areal density, inductive thin film recording heads require smaller track pitch. Pole trimming of conventional heads where P1 width is made equal to the P2 width is suggested in literature as a method for increasing the track density. A patented design called the bevel head where pole P1 of the conventional head is beveled to have the same width as P2 width at the gap, is shown to have equivalent offtrack performance as the pole trimmed heads. The bevel heads require a simpler process to manufacture compared to the pole trimmed heads. Three dimensional field maps are computed for conventional heads, pole trimmed heads and for the beveled heads at different values of write currents. Using these field maps, a simulation of the recording process is done to compute the erase width, write width, read width and isolated pulse response. Both pole trimmed heads and the bevel heads show improvement over the conventional heads in accomplishing a narrower erase width. An offtrack capability model is developed to fit the experimental 747 curve based on the microtrack profile, erase width and a SNR value. Using this model, track density is calculated for all the three heads. Pole trimmed heads and bevel heads show a similar improvement over conventional heads in accomplishing higher track density. >

An analysis is given to determine the maximum areal density achievable in digital magnetic recording and the associated optimal bit aspect ratio. Typical transducer-media parameters are selected, a conventional two-path peak detection data channel is modeled, and error probability is determined as a function of track density and bit density so that maximal areal density and optimal user bit aspect ratio can be determined. >

The shielded magnetoresistive (MR) head offtrack profile shows a wide output plateau which follows the conventional offtrack roll off curve. The authors investigated the origin of the unique offtrack characteristics and their influence on crosstalk signal-to-noise-ratio (SNR), based on experimental and magnetic calculation results. In the measurement, 8- mu m track-width MR heads, consisting of a pair of 100- mu m shields and a trilayered MR element between shields, were used. The plateau width is close to the shield width. The output in the plateau region is the sum of the contributed outputs from individual tracks under the shield. Therefore, this output can severely reduce the crosstalk SNR when the MR head includes several tracks under the shield. Magnetic calculation shows that the magnetic flux from the recorded track to the MR element through the shields can produce the output at the plateau region. Further examination shows that crosstalk SNR is improved by increasing the shield thickness and/or by decreasing the shield width. Therefore, to realize high track density, shield optimization is important. >

A type of monolithic magnetic recording head is introduced. The head design combines the advantages of monolithic heads, composite heads, and metal-in-gap (MIG) heads by novel fabrication techniques. The slider body is all ferrite, the track is embedded in glass, and MIG technology is utilized. A preferred geometry of the track is used to reduce off-track sensitivity. The track can be formed either on the side or in the center of the slider. Details of head design, manufacture, and performance are presented. The MIG enhances high-frequency performance for advanced disk drives which require high bit density in conjunction with high track density. >

Equations are derived that describe the offtrack behavior of magnetic recording heads with inductive-write-wide, magnetoresistive (MR)-read-narrow in the presence of squeeze and erase bands. The resulting model can be used to predict offtrack performance as a function of trackpitch. It is shown that the offtrack behavior can be broken into five regions in the presence of squeeze and erase bands. >

Availability of a standard thin film ring head merged to MR sensor was investigated for perpendicular double-layered media. It was found side-writing or erasure by the wide upper shield of the head took place under unsuitable writing condition which is harmful for high track density. Since a merged type thin film ring head acts like a single pole head with return path of upper shield, the side-writing by the upper shield appears at excess writing current. However the influence was found to be negligible by optimization of the recording MMF and head pole structure.

We developed a new technology for writing and reading a tape which shows good perspectives for very high track density recording. The key elements of this new technology are: - parallel recording of a large number of tracks thanks to a matrix head structure creates macro tracks which are significantly wider than the guardband separating adjacent macrotracks, - optical detection of the magnetic flux flowing in the reading core thanks to Kerr effect allows high transverse resolution and precise track following, - parallel readout of adjacents bits allows efficient electronic crosstalk compensation, - serpentine structure, allows recording of a very large number of tracks on wide tape without requiring stringent precision on tape stability and mechanical positioning.

A track density simulation model for a discrete track medium and an MR/Inductive head was developed based on an iterative geometric signal-to-noise ratio calculation. Using this model, we optimized design parameters of discrete track media related to track density. Our model suggests that discrete track media can achieve higher track density than conventional continuous track media.

In order to improve off-track capability and thus to achieve higher track density, both sides of the upper and lower pole tips of inductive thin film heads were trimmed to become nearly the same in width, through photolithography and ion milling processes at the air bearing surface. The off-track capability improvement attained by the pole trimming was experimentally estimated by performing off-track profile evaluation and "747 curve" measurement. The difference between the effective track width and the upper pole width, which represents the amount of track side writing and side crosstalk effect, was found to be reduced to 68% of that seen in conventional thin film heads. It was also found that the track interval can be squeezed by as much as 1.0 /spl mu/m more than conventional thin film heads, based on the 747 curve comparison. >