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Gains in storage density in magnetic recording have fundamentally been achieved by scaling—reduced geometrical dimensions under the assumption that the recording physics does not change if all dimensions are scaled appropriately. It is becoming clear that evidence of the breakdown of scaling is now seen. We will here discuss ways to break the constraints on magnetic recording set by scaling. In particular, we will discuss energy-assisted recording, domain-wall-assisted recording, and bit-patterned media, with some emphasis on recording system considerations.

The dependence of intergranular exchange interaction on medium SNR was investigated by micromagnetic simulation. It was found that the medium SNR at a high recording density takes its maximum value at the point where the magnitude of the maximum intergranular exchange field is about same as that of the maximum demagnetization field.

For the ever-increasing recording density in hard disk drives, ultra-low gliding height media are required. It is an immense challenge for the tape-burnishing/wiping process of media to reduce the asperities effectively and efficiently while no scratches occur. The purpose of this paper is to characterize and then optimize the tape-burnishing/wiping process as so to minimize the asperities without leaving any scratches on the media surface. A Taguchi experiment design method is adopted to analyze the data and acquire an optimal level combination of process parameters. The resulting optimal combination is practically implemented in tape-burnishing/wiping the several magnetic recording media, which reveals that the average pass ratio of 5 nm glide avalanche testing increases nearly doubly to a level of 96%. Copyright © 2008 John Wiley & Sons, Ltd.

In order to achieve magneto-optical hybrid recording, a new surface plasmon head was proposed, and the intensity distribution of the optical near-field was calculated using a finite-difference time-domain method. It was confirmed that the head has sufficient resolution and efficiency for 1 Tbit/in.2 recording. Simulation confirmed that the head has very high efficiency, so the feasibility of direct coupling the head with a laser diode was investigated. As a result, the practicality of the lensless head was confirmed, and all parts for reading and recording could be placed on a pico-slider.

An improvement of the recording density in a coaxial holographic recording system is described. We employ a new optical setup into our coaxial system, where the numerical aperture (NA) of an objective lens and the data capacity in one page increase up to 0.85 and 135 kbits, respectively. The recording performances are evaluated experimentally and numerically. The obtained results demonstrate that implemented techniques successfully improve the recording density by a factor of 1.5, achieving a raw data density of 270 Gbit/in.2.

For rewritable optical media, overwriting repeatability is a very important index of performance. In HD DVD-re-recordable (RW) media, the direct overwrite (DOW) margin becomes narrower than that in conventional rewritable media, because the recording density becomes high. Therefore, it is difficult to obtain sufficient DOW characteristics by conventional writing power control methods. In this study, we investigate the degradation factor of DOW characteristics in HD DVD-RW media and develop a new writing power optimization method, which involves detection of changes in space level after DOW. As a result of optimizing writing power of HD DVD-RW media by this new method, the partial response signal-to-noise ratio (PRSNR) after 1000 DOW cycles is about 24 in commercial drives, and it is much more improved than that obtained by conventional methods. Accordingly, it is possible to realize optical disk drives with high recording performance for rewritable optical media.

Pinning effect induced by a grainlike structure on top of a TbFeCo recording layer with an Al or Ag underlayer is investigated. We confirm that the pinning effect depends on the surface structure of the recording layer as well as the underlayer. The Al-underlayered TbFeCo medium shows higher recording density during thermally assisted magnetic recording and higher coercivity than those of the Ag-underlayered one. We can observe that only the Al-underlayered TbFeCo medium has the grainlike structure on top of the TbFeCo recording layer, which reflects well a grainlike structure on the Al underlayer's surface. It indicates that the surface profile of not only the underlayer but also the TbFeCo recording layer laminated onto the underlayer is necessary for inducing the strong pinning effect in the TbFeCo magnetic recording media.

A micromagnetic simulator for a single-pole-type (SPT) writing head that takes into account the full interactions between the head core and the recording medium was accelerated by introducing the Fast Fourier Transform (FFT) into all the magnetostatic calculations. This enabled the head field and the recording process on a medium to be simultaneously calculated which is advantageous for designing a perpendicular magnetic recording head and medium system. If the head field strength is sufficiently large to realize saturation recording, the recording performance of the SPT head with a trailing shield was considerably improved by positioning the trailing shield, although the increase in the head's field gradient was slight. This result indicates that the head's field gradient is one of the most important factors for increasing linear recording density.

We reported simulated results of coupled granular and continuous (CGC)-like film, consisting of FePt granular under layer that act as a domain pinning of TbFeCo layer. For further increasing the recording density, grain diameter and period of each grain p have to be decreased until comparable scale with the domain wall width Wd and it causes difficulty to predict the domain structure. Simulated result shows it could be formed on p ≅ Wd (domain diameter Dd = 25 nm), which domain size is suitable to 1 Tbit/inch2. Moreover, we clarified that Dd = 22 nm (it is suitable at 1.33 Tbit/inch2) at the TbFeCo surface and domain shape could be formed even under the condition of p 10kOe) was observed. Furthermore, to elucidate the details of this contribution by interfacial exchange coupling we carried out simulations while varying the values of interfacial exchange constant Aint over wide range. The observed pinning effect can be attributed to interfacial exchange coupling even much smaller value of Aint ( < 0.047 × 10-6 erg/cm) comparing with A of TbFeCo (0.2 × 10-6 erg/cm) and FePt (1.13 × 10-6 erg/cm).

In this study, we introduced the new concept SUL (Soft Underlayer) of PMR (Perpendicular Magnetic Recording) media for the superior recording performance. The recording performance of PMR media with various SUL types were investigated by Guzik spin stand. Our new concept SUL, which was denoted by the modified SAF (Synthetic Antiferromagnetic Coupling) structure, showed more excellent recording properties than those of others. These improved recording performances may be generated by decreased SUL noise and increased filed gradient with new SUL structure. The obtained results indicated that the modified SAF SUL structure can be helpful to high recording density. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

To reduce the overcoat thickness to achieve higher recording density, 2 nm carbon overcoat produced by ion-beam-deposition (IBD) was designed to replace conventional IBD/sputtered-CN dual layer overcoat. Different combinations of overcoat films were deposited with various thicknesses by DC sputter or IBD. Optimized Z-Tol lubricant and additive were coated on the overcoat films. We found that a new designed IBD overcoat with optimized lubricant can effectively decrease the total head-disk spacing interface which results in 1.5 dB OW, 0.4 dB SNR, 0.7 dB SpN and 0.013 dBm Nm, better and higher than the previous design. It also shows promising tribological performance due to the more diamond like structure and higher lubricant bonding ratio.

Multilevel recording with run-length limited (RLL) modulation is a novel way to significantly increase the recording density without changing the optical or mechanical units of current optical disc systems. In this paper, a new efficient 4-ary RLL(2,13) code with special constraint is designed for four-level RLL modulation on read-only digital versatile disc (DVD-ROM). This code can result in alternate multilevel pits and lands on the disc, and reduce the difficulty of multilevel disc replication. Further more, simulation results show the symbol error rate (SER) performance can be improved about 3 dB when the proposed code is used for optical recording channel with partial-response maximum-likelihood (PRML) detection.

Perpendicular recording technology has become the main stream for 130 Gb/in2 HDD products. In this paper, challenges in perpendicular write head are discussed. Design tradeoffs and concerns of narrow-track single-pole heads, trailing shield heads, floating TS heads, and wrapped-around-shield (WAS) heads are discussed. Experimental data show that WAS heads provide good narrow track and high linear density performance. An areal density of 343 Gb/in2 has been achieved at a very aggressive magnetic spacing condition

This paper reviews the recent developments in the area of MEMS-based probe recording technology. Various state-of-the-art scanning probe microscope (SPM) based techniques are briefly introduced, followed by the description of system approaches of MEMS-based probe recording technology and the basic MEMS-based actuation mechanism. Subsequently, current research status in developing MEMS-based probe recording technology with emphasis on storage architecture, MEMS access systems, probe recording mechanisms, and media for terabit per square inch recording density, is reviewed. Lastly, potential research topics and prospects for MEMS-based probe recording technology development are discussed.

It is necessary to improve the SPT head field gradient to achieve an area recording density of 1 Tbit/inch2 in perpendicular magnetic recording. What influence the head field gradient has on medium noise is, however, not clear and we investigated this by numerical calculations using a micromagnetic simulator in this study. we especially focused on the relationships between jitter in transitions, deviation in the transition slope (πa), and the head field gradient. As a result, we found the jitter and deviation in πa decrease with a steeper head field gradient, which results in a decrease in recording media noise.

A next generation technology of magnetic recording is proposed and verified in terms of electromagnetic simulation. Our method is based on all-optical magnetic recording using nano antennas together with particulate media. This novel method can achieve ultra-fast and high-density magnetic recording: the recording speed is about 100,000 times faster than that for conventional technology and the recording density becomes over a few Tbit/inch2. We will evaluate the localized light generated by various nano antennas and discuss the stability of our recording method.

In order to increase recording density in hard disk drives (HDDs), thermal flying height control (TFC) sliders have recently been introduced to reduce the head-disk spacing to less than 2 nm [1]. Slider/disk contacts increase with a decrease in flying height, and consequently, the likelihood of disk failure due to slider/disk contacts increases [2]. Contacts occur predominantly between the thermal protrusion of TFC sliders and disk asperities, which in turn can cause wear and an increase of the temperature at the read and write elements [3-4]. Wear at the surface of the slider can cause loss of the read signal, while high interfacial temperatures can cause magnetic degradation of the read element. The goal of this study is to investigate the effect of asperity size on the plastic deformation and temperature rise of the read/write element due to contacts with disk asperities.

During the past decade, various two-dimensional magnetic recording (TDMR) systems have been considered or developed in order to achieve surface recording density of a few terabits or more per square inch for future promising magnetic recording technologies [1]. In most cases, an effective two-dimensional (2D) signal processing is expected to introduce these TDMR systems because originally these future recording technologies are suppose to make improvements to attain higher areal density towards 10Tb/in2[2]. In this research, a new signal processing scheme for a TDMR system using bit-patterned media (BPM) is proposed for future high areal density recording technologies. This proposed scheme is based on multitrack recording and simultaneous detection schemes for the bit-patterned media recording (BPMR).

We have investigated a circular arc slider with a high flying height that is suitable for optical disc devices to reduce the thickness of the device and to achieve a higher recording density over a wider recording area. Our proposed slider was supported by parallel flat springs to reduce the tilting motions of the slider in the pitching and rolling directions. Two types of slider were examined: (1) a positive pressure slider with a single shallow pocket on the slider surface, and (2) a negative pressure slider with two shallow pockets. The static and dynamic characteristics of our proposed slider were investigated both theoretically and experimentally. It was found that our proposed sliders followed a disc surface with the amplitude of axial runout of 100 μm with a focusing error of 30 μmp-v in the focusing direction and a tilt angle of

Gap length (GL) of reading head is one of the most critical parameters for high-density magnetic recording systems. A novel method is proposed for quantitative evaluation of the GL fluctuation among a batch of magneto-resistive/giant magneto-resistive heads with same structure design. The method works at head-gimbal assembly level and the evaluation can be done with any read/write analysis equipment. The testing process is based on harmonic analysis of the readback signal. The testing system consists of a selected reference head and sample heads for evaluation. A GL variation function is introduced for the evaluation of GL deviation between the reference head and sample head. This method proved to be easy for implementation and results suggest that variation of GL is considerable and has obvious effect on recording performance in high recording density systems.

In perpendicular recording system, the increase of track density is crucial to achieve ultrahigh areal density. At higher track densities, the adjacent-track interference (ATI) arises. In this work, ATI is studied by micromagnetic simulation. Two adjacent tracks are written successively. The track–track distance (TTD) and head–medium spacing are varied to analyze the write and read performance of these two tracks and to investigate the influence of ATI on recording performance. Simulation results indicate that when a track is written first, it is less vulnerable to ATI. ATI is stronger in a track with higher linear recording density. The head–medium spacing plays a significant role in the achievement of low ATI in perpendicular recording system. If the head–medium spacing is reduced to 5 nm, areal recording density above 540 Gb/in 2 could be realized.

A method of heat-assisted magnetic recording (HAMR) is characterized. The recording medium is a high coercitivity, granular and perpendicular CoNi/Pt multilayered film. Emission current from a scanning tunneling microscope (STM) is the heating source. Experiments show that an average mark size of 90–120 nm is achieved. A model for achieving 1 terabit/sq.in. recording density (or a mark size of 25 nm) is proposed to guide future effort.

Demand for increased data storage has resulted in the development of various types of magnetic tape. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal evaporated (AME) tape, for use in linear tape drives. The structure of AME tape is fundamentally different from metal particulate (MP) tape. The goal of this study was to determine the methods and mechanisms associated with failure of AME tapes as well as to investigate the effect of tape cupping and initial edge quality on tape durability in an advanced linear tape drive. It is shown that AME tape exhibits a slightly lower coefficient of friction than the MP. The negatively cupped AME tape demonstrated a greater value of lateral tape motion peak-to-peak amplitude than both of the positively cupped AME samples as well as the MP tape sample. It was found that poor initial tape edge condition plays a large role in debris generation. For these reasons, positively cupped AME tapes with good initial re...

Novel magnetic materials with ultra-high magnetic moment are presented. The Fe/sub 70/Co/sub 30/ alloy is known to have the highest saturation magnetization of 2.45 T in nature. On the other hand, sputtered Fe/sub 70/Co/sub 30/:Pd and [Fe/sub 70/Co/sub 30//Pd]/sub n/ super-lattice films revealed higher saturation magnetization of 2.49 and 2.57 T at room temperature, respectively, while that of a Fe/sub 70/Co/sub 30/ single-layered film was 2.38 T. These values seemed to be acceptable of a main pole material of the write head in the hard-disk drive with an areal recording density above 160 Gbits/in/sup 2/. In addition, these films can be synthesized using a conventional sputtering apparatus as same as a Fe/sub 70/Co/sub 30/ films. Therefore, these films will promise a feasible way for the increase of an areal recording density without any additional technologies, such as a heat assisted recording, contact recording, or further development of the media.

We propose an advanced detection approach based on capacity-approaching constrained parity-check codes and multiple-error-event correction post-processing for high-density blue laser disc systems. Simulation results for an idealized blue laser disc system show that at high recording density, a performance improvement of 1.7 dB is achieved over the standard 17PP code without parity.

The dependence of the coercive squareness S* on the recording characteristics of CoPtCr-SiO2 perpendicular magnetic recording media was investigated. Experimental results showed that the magnetic cluster size dcl, which is evaluated by observing the ac-erased magnetization pattern of media, decreased with a decrease in S*. Ac-erased noise increased with an increase in S*. At a recording density of 1000 kfci, the S/N of a medium with S* of 0.39 was 5 dB higher than that of a medium with S* of 0.44. The recording magnetization pattern was obtained for a medium with S* of 0.39 at a high recording density of 1300 kfci. Thermal decay of the medium became very small for S* of less than 0.37. It was concluded that S* was effective parameter on the recording characteristics of CoPtCr-SiO2 perpendicular magnetic recording media.

Hard disk drives have been showing a 100% annual growth rate in areal recording density. In order to keep this rate in the future, we must overcome the thermal instability problem of the high-density magnetic recording media. Patterned media is a promising candidate for future high-density magnetic recording because it can improve thermal stability and reduce media transition noise. In this review a new method of fabricating patterned media with an artificially assisted self-assembled mask was described.

Recently, for the high recording density technology that aims at recording density of 1Tbit/inch2, heat assisted hybrid recording has been suggested. Near-field optics is one of the important factors for the hybrid recording to shrink an optical spot to a diameter of 50 nm or below. In this study, we analyzed a double layered plasmon antenna for hybrid recording by Finite Difference Time Domain (FDTD). The double layered plasmon antenna was designed on the resonance wavelength which itself depends on the materials and the shape of the antenna. The results of the calculation showed high power intensity and focused optical spot at the nanosize level.

A cylindrical magnetic storage system was investigated and developed, using perpendicular double-layered media with several CoPtCr-SiO2 recording layers and inclined-pad-type heads with a single-pole-type (SPT) writer designed for use with cylindrical media. The fabricated head was capable of stable flight over a rotating cylindrical medium. The inclined-pad-type head had almost the same linear velocity dependence of its flying characteristics as in the theoretical design, and is thought to be a potentially valuable component of cylindrical magnetic storage systems. Composite recording layers of CoPtCr-SiO2/Ru/Pt/Ta deposited on a rotating cylindrical substrate with a soft magnetic underlayer (SUL) had coercivities of 3.9 kOe (medium #A) and 5.9 kOe (medium #B), controlled by varying the SiO2 content, and a squareness ratio of around 1. These properties were almost the same as those of composite recording layers deposited on conventional disk substrates with SULs. The fundamental read/write characteristics of CoPtCr-SiO2/CoZrNb perpendicular double-layered cylindrical media were measured and a D50 value of around 310 kFCI was obtained using medium #B and an SPT writer attached to the inclined-pad-type head. A reduction of the flying height and protective layer thickness is indispensable for further increasing the areal recording density while maintaining sufficient overwrite capability.

Tribology of the disk-head interface in hard-disk drives (HDDs) was reviewed in this article. The HDD has become a very popular device in our life, and been used for some consumer electronics. Tribology is an essential technology for the progress of HDDs. As the flying height of magnetic head has been reduced with increasing areal recording density, disk-head interference in case of contact is one of the greatest concerns for the reliability of HDDs. It is a very important subject of tribology for HDDs to develop the way to keep the head flying stable for avoiding the occasion of disk-head interference, or the way to allow contact without any troubles for recording operation. In future, development of a continuous contact recording system is expected to achieve ultimate magnetic spacing for endless demands to increase recording density.

In the case of an optical recording disk, system information such as address is recorded on a disk as an emboss signal, like wobble signal. Since this wobble signal has a polarized component, in a system using polarization property as is used in magnetic optical disks, if signals are recorded in the wobbled area, RF signal may be subject to modulation caused by the polarized component. Up until now, in order to ensure the quality of recorded signal, different ways have been adopted, such as separating the wobbled area and recording area or separating the frequency bands for wobble signal and recorded signal. For the purpose of improving efficiency of recorded signal within an optical recording disk and increasing recording density, the possibility of increasing density by recording RF signal in a wobble track was explored. The results show that when using an optical system with a laser spot diameter of 0.96 μm and applying the NRZIplus modulation method for wobble signal, it is possible to do wobble recording at a recording line density of 0.96 μm/bit, considering the limit of read-out resolution of the read-out system.

A high-speed and precise focusing/tracking servo system is indispensable for developing a HDTV optical disk camera-recorder. This system is needed for higher data transfer rate and recording density. In this work, we adopted a feedforward control employing the Zero Phase Error Tracking method for the focusing/tracking servo system, and this method reduced residual focusing/tracking errors compared with a feedback system. In addition, we confirmed that the method makes possible obtaining stable recordings and reproduces signals in optical disk systems with the high data transfer rate needed for broadcast use.

This paper reports on a corrosion-resistant spin-valve head (Ta/NiFe/CoNiFe/CuAu/CoNiFe/PtMn/Ta) for a tape recording system. The spin-valve film has a +0.4 V higher electrochemical potential than the conventional spin-valve film (Ta/NiFe/CoFe/Cu/CoFe/PtMn/Ta). The spin-valve head with CoNiFe magnetic layer and CuAu spacer exhibits good corrosion resistance. An investigation of the recording characteristics of the corrosion-resistant spin-valve head with metal evaporated (ME) tapes showed that: 1) the spin-valve head had about 64% of the output voltage of an isolated pulse of the conventional spin-valve head; 2) the carrier-to-media noise (C/N/sub media/) ratio at a wavelength of 0.4 /spl mu/m of the spin-valve head is the same as that of the conventional spin-valve head; and 3) the C/N/sub media/ ratio of thin ME tape with magnetic layer 33 nm thick was maximized at around M/sub r/t=10 mA, where M/sub r/ is the remanent magnetization and t is the magnetic layer thickness. These results indicate that the corrosion-resistant spin-valve head (Ta/NiFe/CoNiFe/CuAu/CoNiFe/PtMn/Ta) for a tape recording system provides high recording density.

The effect of thin Al underlayers for amorphous TbFeCo-based, perpendicular magnetic recording media were studied in a laser-assisted and also in a non-assisted, conventional magnetic recording method. With the insertion of only a few nanometers of Al underlayer underneath a TbFeCo layer, an increase of coercivity was observed and the linear recording density was improved. It is considered that the relatively rough, grain-like surface structure, of the Al underlayer worked as pinning sites for the TbFeCo laver.

Increases in recording areal density have propelled the disk drive industry in the last dozen years. Several studies and research programs strive to accomplish an areal density of 1 Tb/in/sup 2/. At present, the future of the hard disk drive technology appears predicated on monotonic and unbound areal density growth. The system consequences of using large areal densities are the subject of this paper. It is argued that the limited signal-to-noise ratio (SNR) predicted at 1 Tb/in/sup 2/, as well as the extreme mechanical demands on the system, will cause the user capacity not to grow linearly with areal density, as has been the case in the past. This is due, among other reasons, to the increased servo overhead, the increased error-correction code overhead, and the mechanical requirements that compel the reduction of the size of the mechanism. Without casting in doubt the feasibility of magnetic bit recording at 1 Tb/in/sup 2/, scaling laws nevertheless show that there may be limited rewards for the technical efforts directed toward accomplishing 1 Tb/in/sup 2/. Unless the system SNR can be maintained at about 18 dB, areal density gains will not result in proportional user-capacity gains.

We present three-dimensional optical memory using multilayered media. Multilayered media provides higher contrast readout and higher recording density. We analyzed optimum thicknesses in the multilayered medium for a readout system of the memory. We also demonstrated bit data recording and reading in the multilayered medium at high recording density.

Three-dimensional multi-layered optical storage is one of the most promising methods that break the limitation of recording density in optical storage. It stores the bit information onto the multilayered recording planes inside the thick recording medium and realizes the tremendous large recording capacity. This paper describes the recording/reading principles, the systems, and the materials suitable for three-dimensional multi-layered memory. We also present the experimental results that using photochromic organic materials and rhodamine-B-doped and Au(III)-doped PMMA for recording medium.

Organosilane monolayer of 1H,1H,2H,2H-perfluorodecyltrichlorosilane and PFPE lubricant films were deposited on magnetic hard disk surfaces protected with amorphous carbon overcoats, and their frictional properties were investigated by a ball-on-flat tribotester. The thickness of PFPE films having only an immobile layer or both immobile and mobile layers was varied from about 0.6 nm to 4 nm. The friction coefficient of the organosilane monolayer coated surface is comparable to that of the PFPE coated surface with a 1.0 nm thick immobile layer and lower than that of the PFPE coated surface with a 0.6 nm thick immobile layer. The thickness of the lubricant has to decrease to less than 1 nm to further increase recording density. In that case, the mobile portion of PFPE lubricant is negligible. This study suggests that organosilane monolayers (with shorter chain lengths) may be used as an alternate lubricant in hard disk drive systems.

Potentialities of the methods of information processing, distribution, and storage are analyzed. Directions are defined in which optical information media characteristics can be improved. Possibility of using optical media for a long-term storage of digital information is considered.

The basic design and recording performance of advanced probe heads with trapezoidal pole tips are described. Eighty advanced probe heads were chosen to study the effects of different media designs on parametrics and signal-to-noise ratio (SNR) performances. Excellent writability of the advanced probe heads is demonstrated by a series of overwriting (OW) and nonlinear transition shift (NLTS) saturation measurements. Write currents as low as 5 mA/sub o-p/ are required for recording. Excellent OW can be obtained with both high and low OW ratios. Better than -14 dB of NLTS was measured at linear densities as high as 950 KFCI. While OW was observed to be insensitive to media designs under study, NLTS and media SNR were observed to be strongly dependent on the details of media designs. Adjacent track erasure margins of the advanced probe heads were observed to be excellent on both media under study. Minimal side-writing has been observed using the advanced probe heads with trapezoidal pole shape. The advanced probe heads have also been successfully integrated into 80 GB/P perpendicular magnetic recording drives. Finally, linear densities as high as 830 KBPI and track densities as high as 188.7 KTPI were achieved on optimal head/media combinations. Perpendicular magnetic recording at areal densities as high as 145.7 Gb/in/sup 2/ have thus been demonstrated.

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.

In the advanced tape drive systems which achieve a higher recording density, the wear of rotary heads should be decreased to obtain a higher reproduced output signal by decreasing the ‘Gap depth’ of heads, keeping enough life time. By using the heads made by two kinds of crystal directions of Mn–Zn ferrite and metal evaporated tapes with DLC coating, temperature and humidity dependences of head wear are investigated. The wear rates of both crystal direction heads increase with the decrease in temperature. The wear rate of a (110) head increases very quickly at low temperature, compared with a (100) head. These temperature dependences of head wear are caused by the temperature dependence of the elastic modulus of the tape and the temperature dependence of the friction coefficient between the tape and the head.

Theoretical analyses have projected perpendicular recording capable of achieving ultimate areal densities greater than longitudinal recording systems. For perpendicular recording to supplant longitudinal recording, laboratory demonstrations will need to be made which intercept or exceed the areal densities achieved by state-of-the-art longitudinal recording demonstrations. Recent demonstrations have come close to eliminating the gap between these technologies. In this paper, recording experiments at areal densities in the 60 to 100 Gb/in/sup 2/ range will be described. It will be shown that the head field from conventional single-pole writers is not well localized to the data track and that if the media do not have sufficiently high nucleation thresholds, this fringe field will gradually erase data on the adjacent track if the track pitch is too aggressive. Extension of this technology to densities of the order of 1 Tb/in/sup 2/ will require heads that reduce the extent of the fringe field without sacrificing available on-track field.

Achieving 1-Tb/in/sup 2/ magnetic recording areal density requires head-media spacing (HMS) to be no greater than 6.5 nm. It begs the question whether this is a reality (or physics)-based target. This paper examines the main functions and requirements of each HMS component, overcoats on media and head, lubricant film on media, and head-disk mechanical separation, to explore the feasibility of this 6.5-nm HMS budget. From the analysis one may conclude that, although extremely challenging and involving major paradigm shifts, this target does not appear to be completely out of bounds of physical limits. One HMS budget scenario has been proposed which allocates 1 nm each for disk overcoat, head overcoat, and disk lubricant film, leaving 3.5 nm for head-disk mechanical separation. Two fundamental strategies to achieve 3.5-nm head-disk mechanical separation were also discussed.

In this Letter an original method is proposed to assist optical coupling in energy-assisted magnetic recording systems by introducing a microfocal lens. Simulation results show that the lens effectively reduces the incident light spot size to subwavelength scale, which benefits the magnetic recording density. The proposed microfocal lens can be manufactured at low cost because its fabrication is compatible with the conventional magnetic read/write head process.

Volume recording is the key to increase optical storage density. Disc transparency requires the pits of each layer to generate very small phase shift to the transmitted beam. Readout of very shallow phase shift has been proven possible, and new tracking methods have been designed. We showed that focused recording can work up to a few hundred layers with good power efficiency and realistic optical design; this should pave the way up to multi-terabyte optical disc.

It is believed that areal densities approaching one terabit per square inch will ultimately be achieved with conventional magnetic recording technology. Such densities require that very sharp transitions be written on well-defined extremely narrow tracks in a very finely grained thermally stable recording medium. These requirements drive the key characteristics and geometries of the read and write heads and of the recording medium itself. This paper re-examines several aspects of a proposed terabit per square inch recording system and discusses some of the critical technologies required to support such extreme areal densities. These include the necessity of very low magnetic spacing, the ability to fabricate very narrow-track write/read heads, and the need for exquisite track-following capability. One of the biggest challenges at these extreme areal densities will be to develop a recording system that can also deliver very high data rates.

With the increase in recording density, any accumulation on slider surface can cause serious problems, such as high fly–stiction and extensive slider–disk interaction. Therefore, how to mitigate the accumulation on slider surface and thus, improve the stability and reliability of head–disk interface is becoming an important issue. In this work, a nanothin fluoropolymer overcoat with very good oleophobic and hydrophobic properties was applied on slider surface with a dipping process. Tribological performance, such as fly–stiction, normal stiction, and takeoff and landing processes, of the coated sliders was studied. Test results show that although normal stiction is not lowered, normal stiction modulation is reduced obviously by the overcoat. Fly–stiction and its modulation of coated sliders are much smaller than those of uncoated sliders. Coated sliders show much better takeoff and landing performance during contact start stop tests. After tests, the surfaces of tested sliders and disks were examined with an optical microscope, surface reflectance analyzer, and TOF–SIMS to interpret the tribological performance of the coated sliders. It can be concluded that the fluoropolymer overcoat reduces the amount of accumulation on slider surface and thus, improves the tribological performance of the coated sliders.

Co 85 Cr 13 Ta 2 /Cr/C films for longitudinal recording disks were deposited by plasma-enhanced facing targets sputtering apparatus on 2.5 in and ultra-flat substrates of glass ceramics, to obtain low-noise media for high-density recording systems. In this study, the dependence of the microstructure on the sputtering conditions, such as Ar pressure ( P Ar ) of 0.07 mTorr in the background pressure of 1×10 −7 was investigated. As a result, better microstructure with very loosely, magnetically coupled grains was observed by TEM, compared with that in P Ar of 0.2 mTorr. This suggests that a proposed media is suitable for ultra-high-density recording systems.

High-density recording four times that of a current DVD-RAM has been achieved by applying Domain Wall Displacement Detection (DWDD) technology using a conventional optical head which has the same wavelength of 660 nm and NA of 0.6 as the DVD head. It has been confirmed by using a sampled servo and PRML that a recording density of 15 Gbit/inch2 with a track pitch of 540nm and bit length of 80 nm has sufficient system margin. This means that a capacity of 3 GB on a two-inch-diameter disk is now available for portable use. If applied to a digitalvideo camera, one hour of MPEG2 video contents can be recorded at a transfer rate of 6 Mbps.