Automated optical mass storage system with 3-beam magneto-opticaldisk drives

An automated optical mass storage system (optical MSS) with high-speed magnetooptical (MO) disk drives has been developed. It features a high data transfer rate for writing with the use of the 130-mm ISO standard MO disk, and disk cartridges with high storage efficiency. As the key device, a high-speed MO disk drive has been developed. It provides a high-speed data writing capability of about ten times that of conventional MO disk drives. The optical MSS provides a data transfer rate for reading and writing of 2.1 MB/s, a storage capacity of 250 GB to 1 TB, and an average cartridge handling time of 5 s. From performance simulations, the optical MSS is proved to be applicable to a low-traffic random-access file that stores multimedia data and a high-speed direct-access storage device (DASD) backup file     

Magneto-optical disk drive technology using multiple fiber-coupled flying optical heads. Part I. System design and performance

A novel flying-optical-head data storage technology is described. It is based on a micro-optical recording head that contains a silicon micromachined torsional mirror for high-bandwidth track following. Multiple heads and disks are contained in a Winchester-style rotating disk drive. Single-mode optical fibers provide light delivery to and from the heads. Both polarization-maintaining and low-birefringence fiber systems have been implemented for magneto-optical (MO) recording. A fixed optics module containing a laser diode, MO detection optics, and a 1 x N fiber bundle switch has been developed as an integral part of this new recording architecture. A 5.25-in. (13.33-cm), half-height prototype drive design and its performance are presented.     

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.     

Tunneling magnetoresistive heads for magnetic data storage

Spintronics is emerging to be a new form of nanotechnologies, which utilizes not only the charge but also spin degree of freedom of electrons. Spin-dependent tunneling transport is one of the many kinds of physical phenomena involving spintronics, which has already found industrial applications. In this paper, we first provide a brief review on the basic physics and materials for magnetic tunnel junctions, followed more importantly by a detailed coverage on the application of magnetic tunneling devices in magnetic data storage. The use of tunneling magnetoresistive reading heads has helped to maintain a fast growth of areal density, which is one of the key advantages of hard disk drives as compared to solid-state memories. This review is focused on the first commercial tunneling magnetoresistive heads in the industry at an areal density of 80 approximately 100 Gbit/in2 for both laptop and desktop Seagate hard disk drive products using longitudinal media. The first generation tunneling magnetoresistive products utilized a bottom stack of tunnel junctions and an abutted hard bias design. The output signal amplitude of these heads was 3 times larger than that of comparable giant magnetoresistive devices, resulting in a 0.6 decade bit error rate gain over the latter. This has enabled high component and drive yields. Due to the improved thermal dissipation of vertical geometry, the tunneling magnetoresistive head runs cooler with a better lifetime performance, and has demonstrated similar electrical-static-discharge robustness as the giant magnetoresistive devices. It has also demonstrated equivalent or better process and wafer yields compared to the latter. The tunneling magnetoresistive heads are proven to be a mature and capable reader technology. Using the same head design in conjunction with perpendicular recording media, an areal density of 274 Gbit/in2 has been demonstrated, and advanced tunneling magnetoresistive heads can reach 311 Gbit/in2. Today, the tunneling magnetoresistive heads have become a mainstream technology for the hard disk industry and will still be a technology of choice for future hard disk products.     

After Hard Drives—What Comes Next?

There are numerous emerging nonvolatile memory technologies, which have been proposed as being capable of replacing hard disk drives (HDDs). In this paper, the prospects for these alternative technologies to displace HDDs in 2020 are analyzed. In order to compare technologies, projections were made of storage density and performance in year 2020 for both hard disks and the alternative technologies, assuming the alternative technologies could solve their remaining problems and assuming that hard drives would continue to advance areal density at a pace of about 40% per year, which would result in a two-disk 2.5-in disk drive that stores approximately 40 Terabytes and costs about $40. A major conclusion of the study is that to compete with hard drives on a cost per terabyte basis will be challenging for any solid state technology, because the ITRS lithography roadmap limits the density that most alternative technologies can achieve. Those technologies with the best opportunity have a small cell size and the capability of storing multiple bits per cell. Phase change random access memory (PCRAM) and spin transfer torque random access memory (STTRAM) appear to meet these criteria. PCRAMs are being marketed by at least one supplier and therefore appear to be closer to practical realization. On the other hand, STTRAMs would appear to have a performance edge assuming they, too, can be brought to market with multiple bits per cell. Although there are technologies that are not limited by the lithography roadmap and thus have greater areal density potential, they tend to be further from practical realization.     

Acousto-optic parallel read/write head for optical disk data storage

Parallel read and write of optical disks has traditionally used a static grating for read or a linear array of independent lasers for read and write. Depending on the implementation, these systems suffer from coherent cross talk, excessive space between spots, and an inability to independently track. We show that a dynamic acousto-optic grating can generate multiple parallel read/write spots on the disk, each of which can be independently modulated and tracked and all of which are incoherent in less that a bit period. The resulting disk pickup can potentially reach gigabit per second transfer rates with only a modest increase in the drive complexity.     

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%。     

Superconducting magnetic energy storage

After a brief review of the reasons for and forms of secondary energy storage and of the elements and history of inductive or magnetic storage, we discuss the four distinct areas in which superconducting magnetic energy storage can be applied. Differences in energy transfer times place different requirements on the storage coil, on the switch or transfer element, and on the energy losses in the superconductor. We report on designs and experiments in one of these areas with 2 to 300 kJ units, and on the analysis and plans for an installation that is to provide 250 MJ of plasma compression energy for the theta-pinch controlled thermonuclear fusion test reactor. We point out those elements of inductive storage that need further development before a theta-pinch fusion reactor can become economically competitive. Finally, we compare the size and costs of the energy storage components of these systems with similar and with larger inductive storage systems that are to interact reversibly with electric utility networks.     

Microholographic multilayer optical disk data storage

Micrometer-sized reflection holograms can be written into a rapidly rotating homogeneous photopolymer disk at the focus of a high-numerical-aperture beam and its retroreflection to implement high-capacity multilayer digital data storage. This retroreflection is generated by an optical system with positive unity magnification to ensure passive alignment of the counterpropagating beam. Analysis reveals that the storage capacity and transfer rate of this bit-based holographic storage system compare favorably with traditional page-based systems but at a fraction of the system complexity and cost. The analysis is experimentally validated at 532 nm by writing and reading 12 layers of microholograms in a 125-microm photopolymer disk continuously rotating at 3600 rpm. The experimental results predict a capacity limit of 140 Gbytes in a millimeter-thick disk or over 1 Tbyte with the wavelength and numerical aperture of Blu-Ray.     

超薄磁盘保护膜的制备技术

类金刚石薄膜和氮化硅薄膜都是性能很好的绝缘材料,可以用于对磁盘进行保护,在本文中主要讨论了它们各自的制备方法.随着巨磁阻读写磁头(giant magneto-resistive heads)技术的引入,磁盘的存储密度以每年100%的速度在增加,这就要求磁盘保护膜的厚度要尽量的小,所以对制备方法有一定的要求.对类金刚石磁盘保护膜,可以使用等离子体磁控溅射沉积、磁过滤阴极弧沉积、等离子体化学气相沉积来制备;对氮化硅磁盘保护膜,可以使用射频反应溅射沉积来制备.     

Temperature dependence of the birefringence of optical-disk substrates

Injection-molded polycarbonate substrates are used predominantly in read-only, write-once, phase-change and magneto-optic disks for data storage. The in-plane and vertical birefringences of these substrates adversely affect the performance of optical data-storage systems. The disks are typically expected to operate in the ambient temperature range of 5-50 °C. We have investigated the behavior of the in-plane and vertical birefringences of a polycarbonate disk substrate in this temperature range using a custom-built ellipsometer. This study reveals that the in-plane birefringence changes dramatically within the investigated range of temperatures, whereas the vertical birefringence remains essentially constant. We suspect that the change in birefringence is due primarily to thermally induced stress in the substrate.     

A comparison of bubble and disk storage technologies

The evolution of disk storage technology is examined along with its application in current and possible future disk files. Progress in bubble storage technology is considered, and its merits are assessed as a competing storage technology. Tradeoffs in cost and performance are studied, which can enhance the application of disks and bubbles in computer storage hierarchies. Finally, likely entry points for bubbles in storage hierarchies are identified along with the required advances in bubble storage density.     

Microprocessor applications in disk storage systems

The implementation of a disk drive using a micro-processor has led to capabilities not previously found in such devices. This paper will give a brief overview of the architecture of the disk drive and the traditional control functions that have been assimilated by the microprocessor. It will then discuss these new capabilities which include autonomous fault diagnosis, independent servo and I/O exercising, internal error logging, automatic servo error recovery, adaptive servo features, and architectural flexibility.     

The MD 122 dual 3 Mbyte flexible disk drive

The dual 3Mbyte flexible disk drive provides 6 Mbyte of formatted data storage in a compact package designed for in-built use. The two disks may be inserted or removed independently and share a common double ended spindle. A common actuator is used to position the four recording heads. High areal recording density is achieved using advanced technology recording heads and media in association with a microprocesor controlled environmentally compensated servo positioner. The drive incorporates an intelligent controller which provides sophisticated data handling functions and controls the drive in such a manner that the interface to the host is free of drive dependant parameters.     

Subtle effects of the substrate in optical disk data storage systems

Much attention has been focused on the effects of the disk substrate in optical data storage. In particular, substrate birefringence has been studied extensively because it causes significant problems in magneto-optic systems. We investigate certain subtle effects of the substrate, such as feedback into the laser diode, in compact disk and phase-change systems. Our analysis of the compact disk system led us to discover a new technique for the rapid measurement of the substrate birefringence. We also address the question of how focusing the laser beam through the substrate will affect the depth of focus.     

Origin and control of high-temperature ferromagnetism in semiconductors

The extensive experimental and computational search for multifunctional materials has resulted in the development of semiconductor and oxide systems, such as (Ga,Mn)N, (Zn,Cr)Te and HfO(2), which exhibit surprisingly stable ferromagnetic signatures despite having a small or nominally zero concentration of magnetic elements. Here, we show that the ferromagnetism of (Zn,Cr)Te, and the associated magnetooptical and magnetotransport functionalities, are dominated by the formation of Cr-rich (Zn,Cr)Te metallic nanocrystals embedded in the Cr-poor (Zn,Cr)Te matrix. Importantly, the formation of these nanocrystals can be controlled by manipulating the charge state of the Cr ions during the epitaxy. The findings provide insight into the origin of ferromagnetism in a broad range of semiconductors and oxides, and indicate possible functionalities of these composite systems. Furthermore, they demonstrate a bottom-up method for self-organized nanostructure fabrication that is applicable to any system in which the charge state of a constituent depends on the Fermi-level position in the host semiconductor.     

Three-dimensional holographic disks

We describe optical disks that store data holographically in three dimensions by using either angle multiplexing or wavelength multiplexing. Data are stored and retrieved in parallel blocks or pages, and each page consists of approximately 10(6) bits. The storage capacity of such disks is derived as a function of disk thickness, pixel size, page size, and scanning parameters. The optimum storage density is approximately 120 bits/μm(2).     

Ultrafast nanomagnets: seeing data storage in a new light

Magnetic materials provide the most important form of erasable data storage for information technology today. The demand for increased storage capacity has caused bit sizes and features of the read-write transducers to be reduced to the nanoscale. However, increased storage capacity is only useful if there is a commensurate reduction in the time taken to read and write the data. In this article, the basic principles that determine the behaviour of nanomagnetic materials are introduced and their use in data-storage systems is described. Particular attention is paid to processes that limit the speed of operation of the data-storage system. It is shown that optical pump-probe experiments may be used to characterize dynamic magnetic processes with femtosecond temporal resolution. The macroscopic magnetization of a ferromagnet can be made to precess in response to an optically triggered magnetic field pulse, leading to reduced switching times. Alternatively, an ultrashort laser pulse may be used to manipulate the magnitude of the magnetization on femtosecond time-scales, leading to an ultrafast demagnetization in certain ferromagnets, and providing new insight into magnetotransport phenomena. Finally, the outlook for increased record and replay rates is assessed and the prospect of further use of optical techniques within magnetic data-storage technology is discussed.     

DNA Micro-Disks for the Management of DNA-Based Data Storage with Index and Write-Once–Read-Many (WORM) Memory Features

DNA-based data storage has attracted attention because of its higher physical density of the data and longer retention time than those of conventional digital data storage. However, previous DNA-based data storage lacked index features and the data quality of storage after a single access was not preserved, obstructing its industrial use. Here, DNA micro-disks, QR-coded micro-sized disks that harbor data-encoded DNA molecules for the efficient management of DNA-based data storage, are proposed. The two major features that previous DNA-based data-storage studies could not achieve are demonstrated. One feature is accessing data items efficiently by indexing the data-encoded DNA library. Another is achieving write-once–read-many (WORM) memory through the immobilization of DNA molecules on the disk and their enrichment through in situ DNA production. Through these features, the reliability of DNA-based data storage is increased by allowing selective and multiple accession of data-encoded DNA with lower data loss than previous DNA-based data storage methods.     

Analysis of the Slider Off-Track Vibration Caused by the Aerodynamic Loads Associated With Different Components of a Head Stack Assembly in a Disk Drive

The paper describes a numerical investigation of the problem of flow-induced, off-track vibration of the slider in a disk drive. The flow field was simulated in a 3.5-in, 10 000 rpm disk drive using FLUENT flow-modeling software, which yielded the aerodynamic forces and moments for various components of the head stack assembly (HSA). The finite-element model of the HSA was developed using ANSYS software. Then off-track vibration of the slider caused by the aerodynamic loads of different HSA components was computed. The computations showed that the arm experiences the largest fluctuations of aerodynamic load. However, the loadbeam base region appears to make the largest contribution to off-track vibration of the slider, due to the vortex shedding generated by the side tabs of the loadbeam base region.