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Transition curvature in heat-assisted magnetic recording can limit the linear recording density and reduce the readback signal amplitude. In this paper, we describe a simple model for the prediction of the transition curvature and use the model to determine the heat source location, relative to the write head, that minimizes transition curvature.

Microwave assisted magnetic recording (MAMR) has the potential to realise large gains in areal recording density. The key component enabling this gain is the spin torque oscillator (STO), which is typically located in the gap between the main pole and the trailing shield of the write head.

Microwave-assisted magnetic recording (MAMR) has attracted much attention as one of the promising next-generation ultra-high density recording technologies of hard disk drives (HDDs). MAMR is not only the technology which simply extends the recording density of HDDs but also has the potential of 3D magnetic recording. In this section, in addition to the explanations of the basic mechanism and some of the demonstrations of MAMR, some efforts for 3D magnetic recording based on MAMR technology will be explained.

Structural, morphological and magnetic properties of CoCrPt@(TiO2,CoO) granular thin films deposited on Ru/NixPd100-x/NiTa intermediate layers were investigated as a function of the NixPd100-x composition (x = 20, 50, 80). Using a Ni20Pd80 buffer-layer leads to a significant improvement of the crystallographic texture, grain separation and easy-axis angular distribution with respect to conventional systems using Ru/NiTa as intermediate layers. As a result, a meaningful enhancement of magnetic properties (anisotropy constant, K = 4.1 x 10(5) J/m(3), out-of-plane coercivity, H-c perpendicular to = 470 kA/m, nucleation field, H-N = -115 kA/m) with respect to conventional systems (K = 3.7 x 10(5) J/m(3), H-c perpendicular to = 374 kA/m, H-N = -71.6 kA/m) was achieved, thus indicating that Ni20Pd80 can potentially be used as buffer-layer to enhance the recording density of conventional Hard Disk Drives.

Heat-assisted magnetic recording (HAMR) is being developed as the next-generation magnetic recording technology. High anisotropy granular media such as FePt-C have been demonstrated as HAMR media for ∼2 Tbpsi (terabits per in2) recording density. In order for this technology to reach its full potential of 4–5 Tbpsi, more progress and innovations are needed for the key requirements for HAMR media, including microstructure, design, magnetic distribution, and thermal design. Beyond granular media, heated-dot magnetic recording (HDMR) is planned to extend areal density toward 10 Tbpsi. HDMR combines similar advanced recording layer materials with advanced patterning techniques to fabricate

While the most promising longitudinal recording systems cannot surpass the theoretical limit of about 200 Gb/in2 for areal recording density and the demand for higher densities is permanently increasing, the perpendicular magnetic recording constitutes the realistic issue to the longitudinal one. The perpendicular magnetic recording offers significant advantages, the most important being stronger write and read fields, and therefore the use of media of higher anisotropy, smaller grain size, higher signal-to-noise ratio, and a better thermal stability. Unfortunately, the perpendicular recording has to cope some important physical and technological difficulties. To overcome them, many ingenious solutions were proposed. In this paper the coupled granular/continuous (CGC) media, a subtle association of the continuous and, respectively, granular media, are analysed from the viewpoint of their magnetic and recording properties. The challenges and possible improvements of CGC media are discussed.

The reliability and stability of hard disk drives (HDDs) are especially important as the areal recording density is rapidly increasing and target to 10 Tb/in2 in the future. The vibrations of the head gimbals assembly (HGA) are inevitable by internal fluid flow and external shock impulses. In this paper, a 3-D finite-element model of an HDD is developed. The internal flow-induced HGA vibrations are investigated by a fluid–structure interaction approach. The external shock-induced vibrations of HGA are also analyzed. The investigated filling gases in the HDD include air and helium.

Utilization of phase information can increase the recording density of holographic data storage. In this paper, a transport of intensity equation is introduced to computer-generated-hologram-based holographic data storage, which can obtain the phase datapage while keeping an optical setup simple and compact. Moreover, two defocused intensity distributions for the transport of intensity equation can be simultaneously obtained by using a conjugate beam from the computer-generated hologram.

Today's tape storage systems are widely used as a low-cost solution for data backup and archiving for the rapidly growing amount of digital information produced in various fields. Following the Information Storage Industry Consortium (INSIC) Roadmap [1], tape cartridge capacity continues to scale by doubling the capacity every two years. Developments in read channel technology are expected to play an important role in improving data-storage capability. The introduction of powerful error-correction codes, such as low density parity check (LDPC) codes to the tape storage system (and which have already been applied to current HDD systems) is anticipated to achieve system operation under low SNR conditions, enabling additional increases in areal recording density. However, at a low SNR, a loss-of-lock (LOL) in the phase-locked loop (PLL) will frequently occur in the current timing recovery scheme. Previous studies of the iterative timing recovery scheme [2], [3] enable systems to operate robustly even at low SNR conditions. However, due to the complexity of these systems, the cost of hardware makes it difficult to introduce iterative timing recovery schemes into multichannel tape systems. In this work, it is shown that erroneous feedback in the PLL caused by misdetection of the detector is the major cause for LOL in tape systems at high recording densities. To cope with these misdetections of the detector while maintaining an acceptable latency in the feedback loop, a new timing recovery scheme that utilizes the soft-output information of the detector was studied. The results show that LOL rate performance can clearly be improved by such schemes, with only a small increase in implementation complexity.

A multiplex method of recording computer-synthesised one-dimensional Fourier holograms intended for holographic memory devices is proposed. The method potentially allows increasing the recording density in the previously proposed holographic memory system based on the computer synthesis and projection recording of data page holograms.

Due to ultra-high density, a bit-patterned media recording (BPMR) system experiences two-dimensional (2D) interference--inter-symbol interference (ISI) and inter-track interference (ITI)--which degrades the overall performance of a recording systems. Therefore, we propose a novel single-track equalization and a single track detection that can perform these duties almost equally well. Our novel equalizer design uses ISI and ITI estimation schemes with the help of cross-correlation functions. The simulation result shows that our proposed method is able to achieve a significant performance gain over the one-dimensional (1D) equalization method and the conventional joint-track equalization, especially at higher recording density.

All-optical magnetic recording with localized circularly polarized light is studied for realizing ultrafast and high-density magnetic recording. We design plasmonic cross antennas with bit-patterned media and evaluate the Stokes parameters. Using our proposed method, the magnetic recording speed is about 100,000 times faster than that for conventional methods and the recording density becomes over 2 T bit/inch2.

The effect of offsets between the focused spot positions of two recording beams used in microholographic memory in the in-plane and vertical directions of the recording medium on the readout signal was investigated through a numerical simulation. The tolerance of recording beam offsets, which was defined as the offset when the normalized signal level decreased to 0.8, was determined to be 0.092 and 0.54 μm in the in-plane and vertical directions, respectively, when the wavelength of the laser was 405 nm and the numerical aperture of the objective lenses was 0.85. These values correspond to 16% of the focused spot size. Moreover, when the recording beam offsets were within the above values and the signal-to-noise ratio of 2 was allowed, the bit intervals of 0.15 and 0.75 μm in the in-plane and vertical directions, respectively, which correspond to the recording density of 59 bit/μm3, were shown to be feasible for confocal detection.

The analysis and research of optical disc mastering systems for high density recording has been carried out. The features of design and construction of the systems for recording high density optical disc is considered. Presented conditions increase the recording density of the optical discs. Tabl.: 1. Fig.: 5. Refs: 28 titles.

Heat assisted magnetic recording (HAMR) is a promising choice to surpass the super-paramagnetic limit in magnetic recording and to allow continued increase in the areal recording density of hard disk drive. However, lubricant depletion on disk surface might be a problem in HAMR due to high temperature during writing process. In this work, depletion of four types of commercial lubricants on our HAMR media has been evaluated under equivalent HAMR conditions. Linear relationships between the lubricant depletion depth and the logarithm of the equivalent laser heating time have been established for these lubricants. The depletion depths of the lubricants at different laser heating durations are predicated. It is found that the performance of the four evaluated lubricants is acceptable in respect of lubricant depletion depth by hypothesizing the total heating duration for a given point on the media over the lifetime of the drive is 106 ns.

Optimum structural dimensions and characteristics of a granular thermally-assisted-magnetic-recording (TAMR) medium for a recording density of more than 6 Tb/in2 were investigated by using optical, thermal, and Landau-Lifshitz-Gilbert (LLG) simulators. A sharp thermal profile in the medium could be obtained by using a heat-sink layer with heat conductivity greater than 100 W/m K. The ratio of in-plane κ to out-of-plane κ(κxy/κg) of the recording layer and thickness (TmMgO) of the MgO layer should both be decreased. The targets for magnetic-write width (MWW) and signal-to-noise ratio (SNR) are 18 nm and 12 dB for a recording density greater than 6 Tb/in2, respectively. In the case of TmMgO of 12 nm, the conditions for achieving these targets are ΔT of 450 K and Heff of 1.36 MA/m. In the case of TmMgO of 5 nm, the conditions are ΔT of 600 K and Heff of 1.4 MA/m (namely, MWW of 18 nm and recording density of 6.0 Tb/in2); ΔT of 550 K and Heff of 1.48 MA/m (namely, MWW of 16.5 nm and recording density of 6.5 Tb/in2); and ΔT of 500 K and Heff of 1.58 MA/m (namely, MWW of 15.0 nm and recording density of 7.2 Tb/in2). It is also clear that the thermal profile is a determinant factor in MWW.

Heat-assisted magnetic recording (HAMR) limitations and extendibility are studied in light of the recent 1.0 Tb/in2 technology demonstration. The paper examines HAMR specific technology challenges, including switching field distributions at elevated temperature, saturation noise, and near-field transducer (NFT) thermal spot-size limits. While current HAMR recording density ( ~ 1 Tb/in2) is limited by switching field distribution and thermal spot size, ultimate HAMR density (up to 5 Tb/in2) is determined by achievable recording-layer magnetic anisotropy and grain size.

Magnetic particulate tape media have been increasing their storage capacity per cartridge in linear tape systems. The technological advances in fine magnetic particles, their orientation, surface-profile design, thin magnetic layers, and low total thicknesses have enabled the enhancement of the areal recording density and windable tape length. In particular, the practical use of barium-ferrite particles will continuously contribute to the increase in the storage capacity by improving the recording performance.

Thermally assisted magnetic recording (TAR) with bit-patterned media was investigated by micromagnetic simulation. The media were assumed to be FePt layers. The effective head-field margin as well as the increase in temperature margin and down-track shift margin was investigated. Conditions of the head and medium that lead to a recording density beyond 5 Tb/in 2 were proposed.

This paper deals with the design of the structure and shape of writing probes in alternative electric data storage devices based on electric polarization fields. In order to de sign high recording density electric recording devices, th e shape of the writing probe is optimized using a response surface methodology. The structure of a writing probe is also investigated according to the existence and nonexistence of the electric shield. The static and dynamic characteristic of recording density is analyzed and compared with conventional recording devices based on the magnetic magnetization field.

Heat-assisted magnetic recording (HAMR) is studied to realize a high recording density of over 4 Tbit/in.2. The HAMR process requires light to be concentrated into a small area, which becomes heated on a recording medium. We studied a plasmonic waveguide (PWG) for surface plasmon polariton (SPP) propagation, which can easily cool down the near-field transducer (NFT) at the end of the PWG. It is important for the PWG to efficiently concentrate SPP to the tip of a magnetic head. We analyzed a PWG structure with protection layers, such as diamond-like carbon (DLC) and lubricant layers, to concentrate SPP onto the media and to effectively heat the recording area while keeping the NFT temperature below 100 °C.

This paper proposes a hybrid of multilayer perceptron neural network (MLPNN) and Volterra equalizer (VE) denoted hMLPNN-VE in nonlinear perpendicular magnetic recording (PMR) channels. The proposed detector integrates the nonlinear product terms of the delayed readback signals generated from the VE into the nonlinear processing of the MLPNN. The detection performance comparison is evaluated in terms of the tradeoff between the bit error rate (BER), complexity and reliability for a nonlinear Volterra channel at high normalized recording density. The proposed hMLPNN-VE outperforms MLPNN based equalizer (MLPNNE), VE and the conventional partial response maximum likelihood (PRML) detector.

The geometric and information parameters of the page-oriented holographic memory are optimized with allowance for the cross-talk influence on the recording density and on the bit error rate.

We have investigated magnetotransport properties of magnetic tunnel junctions (MTJ) with rock-salt type ZnO(001) or MgO/ZnO(001) barriers by both calculation and experiments. The first-principles transmission calculations based on NEGF method clarifed that the MgO/ZnO barrier had coherent tunneling through Δ1 state such as a conventional MgO(001) barrier. Experimental results revealed that the MTJs with an MgO/ZnO barrier had an MR ratio of 70% at a low resistance-area(RA) product of 0.5Ωμm2. This MR ratio is almost the same as the MgO barrier or higher. The rock-salt type ZnO(001)-based MTJs seem to be suitable for application to the read magnetic heads of hard-disk drives (HDDs) with an areal recording density of over 500Gbits/in2.

Lithographically patterned recording media are one of the approaches to achieving Tb/in 2 and beyond recording densities. This will require fabrication of sub-10 nm discrete magnetic islands covering a full disk with tight spacing and size distributions and a narrow switching field distribution. To become an economically successful technology, this will need to be achieved with high throughput and low cost. The technology to fabricate such patterned media will need to be developed, and may require innovative solutions such as self-assembly and nanoimprinting, along with improved magnetic thin films for achieving high anisotropy and narrow switching field distributions.

Issues pertaining to the realisation of areal recording densities in excess of 1 Tbit / in 2 are discussed. Using a composite media structure with well defined magnetic and microstructural properties the potential for achieving 1 Tbit / in 2 using existing methodologies is clear. Higher densities will require the use of additional technologies.

The current status of CoPtCr–SiO2 granular media is briefly reviewed, and challenges relative to media technology exceeding 1 Tb/in2 are discussed. It is effective to enhance grain isolation using oxide materials that easily precipitate at the grain boundary, and this technique is adopted in commercially available perpendicular recording media. Although some difficulties such as reduction of the grain size retaining the switching field remain, 1 Tb/in2 could be achieved by using granular exchange-coupled composite-type media or related technologies. Discrete track media could be used for more than 1 Tb/in2 recording. It could also take several years to further develop nano-processing technology and establish a cost-effective infrastructure. BPM offers great potential in achieving high recording density, although some necessary technologies are still too primitive to consider commercial production.

We report the simulated results for coupled granular and continuous (CGC) films for the thermo assisted magnetic recoding, consisting of FePt particles under layers that act as domain pinning sites of TbFeCo layers. As domain size should be smaller to further increase the recording density, the number of FePt grains has to be decreased in the domain. The simulated results demonstrated that they could be formed in a domain as small as 18.3 nm in diameter, which corresponds to a recording density of 1.8 Tbit/inch2. Here, three FePt grains were effective for pinning. We also estimated the effective wall coercivity, Hw, from the simulation varying the applied magnetic field until a domain had shrunk and disappeared. The Hw was over 12 [KOe] where there were only three grains for pinning. The Hw was a function of the radius of the curvature at the pinning point and also the inverse average wall length between the pinning points in the same composite films.

The comparison between the dual gradient recording method (DGRM) and the thermal gradient recording method (TGRM) for thermally assisted magnetic recording (TAR) were investigated using the Landau-Lifshitz-Gilbert equation, which adds a stochastic thermal field to an effective field. The magnetization patterns and read/write characteristics were discussed. It was clarified that the write performance of DGRM was superior to TGRM for achieving a high areal recording density.

Microwave-assisted magnetic recording (MAMR) has been proposed as one of the candidates to achieve a higher area1 recording density over 1.0 Tbit/inch2. MAMR needs a device to generate strong oscillating magnetic field to induce magnetic resonance in a recording medium. Its oscillating frequency is needed over 20 GHz, implying that eddy current might influence the dynamic magnetization behaviors of the field generating layer (FGL). In this paper, the influences of eddy current on the dynamic behaviors of the oscillator proposed by J-G. Zhu are discussed. The eddy current field in the FGL acts on the magnetizations to inhibit the rotation of precession, resulting in a slight increase in the oscillating frequency. However, the strength of the eddy current field is very small less than 20 A/m. Thus, it is concluded that eddy current field little influences the dynamic behaviors of the FGL.

In order to improve the performance and simplify the structure of the conventional detectors in high density magnetic channels, a new equalizer based on bilinear recursive polynomial models, which uses the previously estimated sequence, is proposed. The performance is compared with the conventional equalizers and the maximum likelihood sequential detection bound. The simulation results show that as the normalized recording density becomes higher the proposed equalizer with much simpler structures shows the similar or better performances compared to the partial response maximum likelihood methods and the proposed equalizer is robust to the jitter noise.

Heat assisted magnetic recording (HAMR) is a promising technique to overcome the superparamagnetic limit to further increase the areal recording density of hard disk drives. However, HAMR brings about serious problems to the slider-disk interface, such as lubricant depletion on disk surface caused by laser heating. It is proposed to overcome the lubricant depletion problem by using vapor lubrication. The lubricant film formation process on disk surface in vapor lubrication is studied theoretically based on fundamental adsorption and desorption theories. The controlling parameters of lubricant film thickness and film formation time are identified. It is found that the lubricant film thickness is controlled mainly by lubricant vapor pressure and molecular weight. The film formation time can be shortened by using low molecular weight lubricant and high temperature lubricant vapor.

It is the first report on the recording performance of a perpendicular metal evaporated (ME) tape measured with a giant magnetoresistive head. To solve the application difficulty of oblique evaporated tape media to linear scan tape systems, a perpendicular evaporated Co-CoO tape was proposed instead. The prepared sample showed perpendicular anisotropy with coercivity of 107.3 kA/m, M r t of 3.9 mA and squareness of 0.25. Identical recording characteristics were obtained for both head-media moving directions, which enables the application of perpendicular evaporated Co-CoO tape to linear scan tape systems. The better carrier-to-noise ratio was also confirmed by comparison with a current advanced product of metal particulate tape, which can realize the higher recording density of linear scan tape systems using ME tape. © 2008 Elsevier B.V. All rights reserved.

Perpendicular magnetic recording was a long-awaited technology to break the areal density limit of the longitudinal recording system. Through the research on high squareness CoPtCrO/Ru recording media, we have established the intrinsic design concept of stable perpendicular magnetic recording in which the high nucleation field of perpendicular magnetic media supports the very stable magnetization against disturbance fields in recording processes. By intensive study of the perpendicular magnetic recording integration into the 2.5-in 50-80 GB/platter test hard disk drives (HDDs), we have successfully developed the first 1.8-in 40 GB/platter HDD product featuring the perpendicular magnetic recording technology at 133 Gbit/in2 recording density. Thermal stability and spacing robustness in the writing process of the perpendicular recording system were also found to be great advantages of the future portable HDD systems.

The possibility of realizing linear magnetic recording systems over 15 Gb/in2 recording density has been shown in our test with newly developed metal particulate (MP) tape using 35-nm-size fine metal particles and a GMR head designed for hard disk drive (HDD). It was done under a read-track-base calculation with the following media: magnetic layer thickness =60 nm, surface roughness Ra=2.0 nm.