头/盘界面均匀化Reynolds方程及其高效数值求解

当硬盘工作时,磁头滑块飞行在高速旋转的磁盘上方,头/盘界面产生了一层只有几个纳米的气膜,该气膜润滑方程为考虑气体稀薄效应的修正Reynolds方程。为了提高磁记录密度,人们正在考虑用离散磁道（Discrete Track Recording,DTR）磁盘取代传统的光滑磁盘。由于这种DTR磁盘表面磁道和沟槽的影响,在数值求解修正Reynolds方程的过程中,就需要足够多的离散网格来分辨出DTR磁盘表面几何形状,从而带来了计算效率问题。基于均匀化理论和修正Reynolds方程的线性流率（Linearized Flow Rate,LFR）模型,该文推导了一个适合分析DTR磁盘气体润滑特性的均匀化Reynolds方程,并采用有限体积法对均匀化Reynolds方程进行了求解和验证。其结果显示:相对于修正Reynolds方程,求解均匀化Reynolds方程只需要很少的离散网格,从而节省了大量的计算时间,大幅提高了计算效率,且两者压力分布、压力中心和承载力的最大相对误差都小于3.5%。     

Study of Lithographically Defined Data Track and Servo Patterns

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

Study on micro-structure and morphological evolution of Fe/Pt nano-magnetic film

One of the vertical magnetic recordings medium materials of the hard disk drive (HDD) is a Fe/Pt thin film. The development of ultra-high density magnetic recording medium in next generation is expected the magnetic disks such as HDD with capacity enlargement of the data. In order to study effectiveness of the proposed sputtering method, we evaluated micro structure, magnetic and the mechanical properties of a Fe/Pt thin film by some sputtering process conditions. From research results, effect sputtering conditions on micro-structure and mechanical properties of Fe/Pt nano film are verified.     

Fabrication of Flyable Perpendicular Discrete Track Media

Discrete track media offers many potential recording advantages over conventional continuous media in hard disk drives. In this study, we present a novel fabrication process for discrete track perpendicular magnetic media via electron beam lithography, ion milling, and the use of a protective Al sacrificial layer. Physical characterization of the media confirms the process is able to produce patterned tracks with no damage to the media. Spin stand analysis verifies the disks are flyable and capable of recording sharp transitions without any degradation in the magnetic signal     

Collinear holography

A novel reading and writing technology for a holographic storage system called collinear holography is developed. With this method, two-dimensional page data can be recorded as volumetric holograms generated by a reference beam and a signal beam that are bundled on the same axis and irradiated on the recording medium through a single objective lens. The multiplex recording and reconstructing process is demonstrated, and it is presented that optical configuration and the dichroic media disk structure are suitable for a compact system. This method enables us to construct a small volumetric optical disk storage system with CD and DVD upper compatibility.     

5.25 inch floppy disk drive using perpendicular magnetic recording

5.25 inch high density perpendicular magnetic recording floppy disk drive has beer developed by employing new types of high saturation magnetization ring head, Co-Cr single layer medium with Ge underlayer, head slider with ellipsoidal surface configuration to assure intimate head to medium contact, and signal equalization. By these combination, recording density D50 of 145 kFCI, peakshift of 28 % at 100 kFCI, signal to noise ratio of 40.4 dB for cut-off frequency 4.25 MHz, overwrite signal to noise ratio of 27 dB, measured by writing signals at 48 kFCI over previously written 100 kFCI signals were obtained as typical recording characteristics. These results would indicate that floppy disk drive with 100 kFCI recording density has enough system margin by above-mentioned combination. In this paper, design and performance of newly developed floppy disk drive are described.     

Collinear technology for a holographic versatile disk

A novel reading and writing technology for a holographic versatile disk (HVD) system called collinear technology is developed. With this method a two-dimensional data page can be recorded as volumetric holograms generated by a reference beam and a signal beam that are bundled on the same axis and that are irradiated on the recording medium through a single objective lens. The multiplex recording and reconstruction process is demonstrated, and it is shown that the optical configuration and the dichroic medium disk structure are suitable for a compact system. With the HVD's special structure, the system can use a servo to focus, track, and locate the reading and writing addresses. A unique selectable-capacity recording format of a HVD and its standardization activity are also introduced. This method willenable us to construct a small HVD system with CD and DVD upper compatibilities.     

Aberration-corrected transmission electron microscopy of the intergranular phase in magnetic recording media

In perpendicular hard disk memory media, nanometric magnetic Co-rich grains are separated by a ～1 nm thick nonmagnetic and preferably amorphous intergranular phase (IP). Attempts at observing the IP structure at high resolution using TEM have been obstructed by the superposition of lattice fringes from the crystalline grains extending into the IP region in images. Here we present the first images of a magnetic recording medium produced using a spherical aberration-corrected TEM showing the true amorphous IP structure in contrast to the crystalline grains, allowing the accurate determination of the grain-IP interface and the grain and IP dimensions. It is shown that these aberration-corrected TEM images are functionally superior for analyzing certain features of the ultrahigh capacity data recording media.     

磁头与离散磁道式磁盘瞬态接触行为研究

 离散磁道式磁盘在与磁头瞬态接触过程中极易损坏.为改善离散磁道式磁盘的瞬态接触状况,采用有限元仿真方法,建立了平整化前后离散磁道式磁盘与磁头的瞬态接触模型,分析了平整化前后离散磁道式磁盘接触应力分布特点,研究了磁头冲击速度、径向速度、磁盘表面摩擦系数等接触条件及平整化对离散磁道式磁盘最大等效塑性应变、塑性应变总体积的影响.结果表明：磁头冲击速度、寻道速度增大均可导致磁盘最大等效塑性应变、塑性应变总体积增大;摩擦系数增大可增大磁道最大等效塑性应变、减小塑性应变总体积;在接触初期,平整化离散磁道式磁盘可以减小磁道最大接触应力,缓解应力集中现象;在接触全过程中,平整化离散磁道式磁盘可以减小磁道最大等效塑性应变及塑性应变总体积;平整化所用2种弹性模量等力学特性不同的填充材料,即磁道材料与类金刚石碳,对于磁道接触状况的改善作用区别较小.以上结论可为降低离散磁道式磁盘的破坏程度提供理论指导．     

The Feasibility of$+15$Gb/in$^2$High-Density Recording With Barium-Ferrite Particulate Media and a GMR Head

The feasibility of a high-density magnetic particulate recording medium with a thin magnetic layer of evenly dispersed high-coercivity barium-ferrite particles was investigated. Thermal stability, writability, and an areal recording density of 17.5 Gb/in$^2$were confirmed for a flexible disk system using a giant magnetoresistive head.     

Recording performance of discrete track patterned media fabricated by focused ion beam

We report on the recording performance of discrete track patterned media fabricated by focused ion beam (FIB). We investigated performance over a small area by spinstand read/write testing. Discrete track patterned regions show smaller magnetic track width and better signal separation between adjacent tracks and therefore higher track density than that of nonpatterned continuous media as a result of reduced side fringe effect and edge noise. We found that, at a designed groove depth of 4-8 nm, the shallow FIB etched grooves already provide good isolation between adjacent tracks, indicating the superiority of ion beam induced modification of magnetic properties in film media over physical modification of disk surface topography. This has implications for discrete track recording and media fabrication.     

Extremely high bit density recording with single-pole perpendicular head

Since perpendicular magnetic recording is free from recording demagnetization, high-density recording up to the intrinsic limit of a recording medium is possible. This prediction was verified experimentally in a flexible disk system using a single-pole head and a Co-Cr/Ni-Fe double-layer medium. We could record and reproduce signals up to 680KFRPI. The recording bit length at the highest density was of the order of the Co-Cr columnar diameter.     

A new W-shaped single-pole head and a high density flexible disk perpendicular magnetic recording system

A new single-pole head with no auxiliary pole was developed for perpendicular magnetic recording. The head is called WSP head (W-shaped Single Pole head) because the head has a W-shaped side core which contributes to increase the recording and reproducing sensitivitiy. The head field of the new head has the same distribusion as that of an auxiliary pole head[1]. The recording and reproducing sensitivity of the head is equal to or higher than that of a ring-type video head. The head eliminates mechanical problems which prevent its application in perpendicular magnetic recording because we can locate the head on one side of the recording medium. As a possible application of the WSP head, a 3 1/2-inch flexible disk recording system was constructed. A linear recording density of the flexible disk system was 65.5 kbits/inch. This density is equivalent to 8 times that of the existing high-density 3 1/2-inch micro-floppy and 11 times that of a 5 1/4-inch floppy disk. In termes of information storage, this density gives a 4 megabyte unformated capacity on one side of a 3 1/2-inch flexible disk. The overwrite signal-to-noise ratio was greater than 30 dB and the peakshift displacement was less than 10 % at the linear dinsity of 65.5 kbits/inch.     

Not just another self-consistent magnetic recording model

A self-consistent magnetic recording modeling method is presented which has proven useful in recording channel design on thin media. Improvements in the magnetic model and in the mathematical treatment stabilize the iterative process and reduce computer storage requirements. Major and minor media loops are fitted to quickly computable bipolynomials. Mathematical improvements include using a strong band diagonal demagnetization matrix, analytic integration with quadratic magnetization fitting, and Newton-Raphson iteration, which gives rapid convergence without underrelaxation. Quantitative predictions of timing errors in 16-bit modified frequency modulation (MFM) data patterns on a 350-bit/mm, 20-track/mm disk memory are presented, as well as playback amplitudes and saturation currents. Predictions can also be compared with experimental read/write data to determine system parameters. Two examples are given: the inference of the head efficiency and of the effective high-frequency medium squareness.     

Model for demagnetization-induced noise in thin-film magneticrecording media

A linear, statistical model is described which predicts the power spectrum of measured noise in bulk-demagnetized (i.e. AC-erased) thin-film magnetic recording media. It is shown that the noise is the result of magnetic flux which is ascribed to erasure-induced transitions along the track length in the medium. The noise power spectrum for a rigid disk medium is shown to correspond to the power spectrum of Poisson-distributed induced transitions along the track length, while noise along the track width is sufficiently described in terms of a uniform, average magnetization with small variance. Experimental data from two thin-film disks are used with the model to estimate the Poisson parameter for each disk. It is demonstrated that AC-erased noise from particulate media can be considered as a limiting case of the Poisson model     

Nanoindentation and the tribology of head-disk interface components

Nanoindentation data are presented for three different but interrelated components of the thin film disk magnetic recording system-the air bearing slider/recording head, the disk substrate, and the sputter deposited thin film disk recording medium. Hardness traces across the slider trailing edge demonstrate the hardness of the NiFe, sputtered Al₂O₃, and the ceramic Al₂O ₃/TiC are 8, 10 and 24-40 GPa, respectively. Lapping under non-optimum, aggressive conditions can lead to significant recession in these components which is directly related to their hardness. The hardness and modulus have been measured for a number of alternate substrate materials ranging from AlMg/NiP to glass and glass ceramic. The ability of these substrates to resist damage from slider shock forces is presented and generally increases with substrate hardness, although other criteria (fracture toughness and plasticity initiation) rue required to rationalize all the data. Finally, hardness and modulus of carbon overcoat films are presented which have been sputtered under various conditions. The process variations lead to variations in hardness, the hardness/modulus (H/E) parameter, and tribological performance in slider/disk testing. The applicability of these mechanical property parameters to the wear degradation is discussed     

Growth of Magnetic Disk Drive Industry and Future

1. IntroductionThe growth of personal computers (PCs) and theexpansion of information networks, featured by theInternet, lead to information storage demand surprisingly. No data storage equipment other than magnetichard disk drives (known as HDD) is able to offer a costperformance that matches the requirements of growing digital network era.Areal recording density of the HDD has been improved more than 3 million times, since RAMAC firstshipped in 1957. During the periods, there were many…     

磁性载体记录的稳定性探索

本文总结了有关贮存在各种磁性记录载体中信息的保存性的一些基本科学技术知识，包括：录音带，录像带，计算机磁带，软磁盘，硬磁盘，光磁盘等，全文分两期登出，本期登其第一部分，内容主要为：磁性记录材料的特性和稳定性，磁性粒子，下期内容为：粘合剂，聚酯带基，环境因素影响等。     

磁场调制直接重写磁光存储介质的记录特性研究

用直流共溅射方法制备了富稀土－过渡族金属非晶态合金薄膜，用数值计算的方法计算了激光照射下多层膜结构盘片的温度场分布，分析了盘片材料成分和结构对热磁记录的影响，对盘片结构进行了优化设计并选定了合适的磁光层和电介质层厚度。实验盘片可在低偏场和低激光功率下记录，盘片的读写性能基本符合２．５英雨可擦重写磁光盘（ＭｉｎｉＤｉｓｋ）的使用要求。     

Fabrication and MFM study of 60 nm track-pitch discrete track media

Discrete track magnetic recording media with a 60 nm track pitch and prewritten servo patterns were fabricated and tested for read/write performance, and a feasibility analysis of the embedded servo was performed. The fabrication process consisted of ultraviolet nanoimprint lithography (UV-NIL) and sequential ion beam etching on a conventional perpendicular magnetic recording medium. Magnetic patterns were written to the fabricated tracks at 700 kilo flux changes per inch (kFCI) using a spin stand and were read using magnetic force microscopy (MFM), with a resulting signal-to-noise ratio (SNR) of 12.15 dB. The servo pattern was also visualized with MFM. These results demonstrated the feasibility of writing to a 30 nm wide discrete data track and the workability of the embedded servo pattern.