Polymer film selection for corrosion protection of data storage magnetic materials

Due to the current requirement of high recording density of hard disk drive, the thickness of DLC layer which is the protective layer is needed to be reduced. Therefore, the corrosion of read-write elements that are fabricated from soft magnetic materials is more critical. During the photolithography process, polymer photoresist is playing the major role on controlling the corrosion of soft magnetic materials. Two different types of polymer photoresists are selected to investigate, noted as wet photoresist and dry photoresist, respectively. Contact angle measurement, AFM and SEM are techniques using to determine the quality of polymer photoresists. Furthermore, the direct corrosion is also studied by using potentiostat/galvanostat-based measurements. The result suggested that the wet photoresist, AZ4999 Clariant, is better as compared to that of dry photoresist. No surface degradation as well as surface defects of the wet photoresist was found after lithography process. The corrosion rate of the specimen coated by this corresponding wet film is found to be only 1.44 x 10(-6) mm/y. In addition, the wet photoresist surface is hydrophobic posed of more than 75 degree of contact angle.     

Inorganic materials for optical data storage

Recyclable holographic (optical) storage in inorganic materials is nowadays possible due to the advent of laser. Various performance parameters of the state-of-the-art of optical storage are discussed in detail with reference to the well-established case of ferroelectric lithium niobate (LiNbO₃). Various physicochemical techniques are employed in understanding the microscopic mechanisms responsible for optical storage in LiNbO₃. A short summary of other inorganic materials capable of holographic storage is also presented.     

Phase-change materials for rewriteable data storage

Phase-change materials are some of the most promising materials for data-storage applications. They are already used in rewriteable optical data storage and offer great potential as an emerging non-volatile electronic memory. This review looks at the unique property combination that characterizes phase-change materials. The crystalline state often shows an octahedral-like atomic arrangement, frequently accompanied by pronounced lattice distortions and huge vacancy concentrations. This can be attributed to the chemical bonding in phase-change alloys, which is promoted by p-orbitals. From this insight, phase-change alloys with desired properties can be designed. This is demonstrated for the optical properties of phase-change alloys, in particular the contrast between the amorphous and crystalline states. The origin of the fast crystallization kinetics is also discussed.     

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.     

Exchange coupling and its applications in magnetic data storage

The continuing scaling of magnetic recording is facing more and more scientific and technological challenges because both the read sensor and recording bit are approaching sub-50 nm regime with the ever increasing areal density in hard disk drives. One of the key and indispensable elements for both high-sensitivity sensors and high-density media is the exchange bias between a ferromagnetic and an antiferromagnetic layer or the exchange coupling between two ferromagnets via a non-magnetic spacer. In the nanometer regime, the exchange coupling between ferromagnet and antiferromagnet or two ferromagnets through a conductive spacer is governed by the intergrain exchange interaction which has its origin in electron spins. Interlayer exchange coupling in multilayer or trilayer essentially originates from the quantum confinement effect. In this paper, we first review the physical origin and various theoretical models of the two types of exchange couplings, followed by a review of the applications of the exchange bias and interlayer exchange coupling in data storage with emphasis on the advanced read sensor and advanced media including perpendicular media and patterned media.     

Improvement of photopolymer materials for holographic data storage

Photopolymer materials are practical materials for use as holographic recording media due to the fact that they are inexpensive, self-processing materials with the ability to record low loss, highly diffraction efficient volume holographic gratings. In general these materials absorb light of an appropriate wavelength, causing photo-polymerization of the local monomer, inducing a change in the material’s refractive index. These small changes in refractive index enable the storage of large quantities of data using holographic techniques. In an attempt to further develop the data storage capacity and quality of the information stored, i.e., resolution, in such materials, a deeper understanding of the photochemical mechanisms present during the formation of holographic gratings has become ever more crucial. From this understanding the response of an acrylamide/polyvinylalcohol based photopolymer to high spatial frequency information is improved through the addition of a chain transfer agent, i.e., sodium formate, HCOONa.     

基于STM/AFM技术的信息存储材料研究现状及进展

信息技术的发展要求存储器件必须具备超高存储密度、超快的存取速率，因而能在纳米尺度上实现信息存储功能的新型超高密度信息存储材料已经成为信息技术领域的研究热点。简要地介绍了近年来利用扫描隧道显微镜／原子力显微镜（STM／AFM）实现信息写入的纳米信息存储材料的研究进展，并进一步列举了尚待解决的问题。     

Optical response of photopolymer materials for holographic data storage applications

We briefly review the application of photopolymer recording materials in the area of holographic data storage. In particular we discuss the recent development of the Non-local Polymerisation Driven Diffusion model. Applying this model we develop simple first-order analytic expressions describing the spatial frequency response of photopolymer materials. The assumptions made in the derivation of these formulae are described and their ranges of validity are examined. The effects of particular physical parameters of a photopolymer on the material response are discussed.     

Chalcogenide glasses as prospective materials for optical memories and optical data storage

This paper first reviews recent progress in the understanding of the nanometer-scale mechanism of reversible photostructural changes in chalcogenide glasses, and its relevance to various photo-induced phenomena. Then the principles of phase-change optical recording are described. Finally, a novel technique for overcoming the diffraction limit in optical recording is considered, namely the super-resolution near-field structure. This technique, used in combination with multicomponent Te-based chalcogenides as a recording medium, is believed to be a prototype for future optical-storage devices.     

Kinetic study of selenium used as optical data storage and holographic recording materials

A kinetic study has been performed on selenium for isothermal and continuous heating processes. The activation energy (E _a) and Avrami exponent (n) have been evaluated in the range 414 to 449 K for the isothermal process and at a heating rate of 5 to 40 K min^–1 for continuous heating. A new iterative calculation to give exact values ofE _a andn for a continuous heating process is also presented.     

Data storage in 2000-trends in data storage technologies

Recent projections by experts in computer systems and semiconductor technology indicate that in the year 2000, personal computers will have a processing speed of 100 million instructions per second and a semiconductor RAM capacity of 1 Gbyte. To work with such a system, data storage devices will need to provide more than 10 Gbytes of capacity and a data rate of 100 Mbyte/s. The advances required by magnetic and magnetooptical disk drives to meet these requirements are examined. Plausible system configurations for achieving these goals are described. A magnetic disk drive utilizing eight 3.5-in. disks on one spindle appears to be a possible configuration. Because of a larger areal density, a magnetooptical disk drive could meet the capacity requirements with only a single 3.5-in. disk. On the other hand, achieving the 100-Mbyte/s data rate and access times comparable to those of magnetic disk systems will require some technological breakthroughs. Without these breakthroughs and assuming magnetic disk progress as expected, magnetooptical disks are expected to provide many of the functions which floppy disks provide today-transfer of programs and databases between systems and economical offline storage     

Superconducting magnetic energy storage

An investigation into the application of superconducting magnetic energy storage for large particle accelerators, and to peak shaving in a power network, where efficiency is improved over the hydro-pumped storage stations already widely used.     

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.     

Superconducting magnetic energy storage

The author presents the rationale for energy storage on utility systems, describes the general technology of SMES (superconducting magnetic energy storage), and explains the chronological development of technology. The present ETM (Engineering Test Model) program is outlined. The impact of high-T_c materials on SMES is discussed. It is concluded that SMES is marginally competitive with other storage technologies and is likely to remain so     

Fluctuation aftereffect in magnetic materials

Time dependence of magnetization under constant field conditions is exhibited by all materials subject to hysteresis. The phenomenon is a consequence of thermal activation of irreversible magnetization effects from metastable to stable states. Experimental observations of time dependence may be accounted for by considering distributions of the energy required for activation of the metastable states. Two simple cases are considered in this paper. The first involves a fixed value activation energy distribution; the second is concerned with magnetization events that all have the same value of activation energy. The latter is applicable to describing magnetization of magnetooptic films. It is shown that the results of measurements of time dependence of magnetization over wide ranges of time and field are useful in distinguishing between different mechanisms involved in magnetization reversal processes     

Current-induced torques in magnetic materials

The magnetization of a magnetic material can be reversed by using electric currents that transport spin angular momentum. In the reciprocal process a changing magnetization orientation produces currents that transport spin angular momentum. Understanding how these processes occur reveals the intricate connection between magnetization and spin transport, and can transform technologies that generate, store or process information via the magnetization direction. Here we explain how currents can generate torques that affect the magnetic orientation and the reciprocal effect in a wide variety of magnetic materials and structures. We also discuss recent state-of-the-art demonstrations of current-induced torque devices that show great promise for enhancing the functionality of semiconductor devices.     

储氢技术及其关键材料研究进展

氢能是未来能源结构中最具发展潜力的能源载体,氢的廉价制备、安全高效储送以及大规模应用是当今研究的重点,而氢能的储存是其中的关键性问题.本文综述了目前主要的储氢技术和储氢材料,如高压气态储氢、低温液态储氢、合金储氢、有机液体氢化物储氢、碳质材料储氢和金属有机骨架类聚合物储氢等,并对未来的研究方向进行了展望.