Magnetic memory disk

An ultraprecision lapping on magnetic memory disk substrate of glass by fixed abrasives in newly developed microspherical cell Yoji Tomita, Tanaka Co. Ltd, Japan and Hiroshi Eda, Ibaraki University, Japan... 

Figure 4-5 Spinel-enstatite glass-ceramic as a magnetic memory disk substrate, in comparison to a canasite disk and a nickel-spinel glass-ceramic.

High modulus is important, e.g., E = 2.1 X 10 psi (14.5 GPa), because stiffness prevents flutter of the magnetic memory disk at high rotational speeds, e.g., 5000-10,000 rpm. 

The question as to whether and to what extent and in what area optical mass storage would replace magnetic systems (disk, tape) was controversially being discussed in the 1980s. In spite of all predictions of an imminent substitution, as of late 1994 magnetic hard disks stiU are the system of choice for computer-dedicated mass storage due to their speed (access time, transfer rate), physical size, and energy consumption this is especially tme when memory-intensive appHcations are mn which use the hard disk as virtual memory. 

There is no competitive situation for data storage disks with embossed iaformation (CD-ROM) and recordable/nonerasable disks (WORM) no counterpart to CD-ROM and WORM exists among magnetic memories. EOD drives are best compared to floppies and removable hard disk media given their possibiUty of easy and problem-free disk exchange and a capacity on the order of that of removable magnetic media (Tape, Bernoulli, SyQuest). 

Electrically Functional. Refractory coatings are used in semiconductor devices, capacitors, resistors, magnetic tape, disk memories, superconductors, solar ceUs, and diffusion barriers to impurity contamination from the substrate to the active layer. 

Optical memory devices such as compact disks (CDs) and digital versatile disks (DVDs) are becoming essential items of audio and visual media as well as of external computer memory media. In these devices, a laser beamis used to record and read information. Because the laser spot can be focused to within a 1 fxm scale, optical memory can access higher density and capacity than conventional magnetic memories can. 

Beall G.H., "Magnetic Memory Storage Device and Disk Having a Glass-Ceramic Substrate," U.S. Pat. No. 5 744 208, 1998. 

Hydrogenated carbon films have been used in the magnetic recording industry as protective overcoats for both memory disks and pickup sliders for many years now. Recently, the inclusion of nitrogen in these films has become of interest, perhaps primarily because it improves the spreading of lubricants on the overcoats. Raman spectroscopy is currently a major quality control tool for carbon overcoats, especially on computer disks. 

The most important mass memories use magnetic media in the form of magnetic tapes or disks (floppy disk and hard disk). Laser addressed optical mass memories are of increasing commercial importance. 

The acceptance of optical data storage iato the mass storage market, which is as yet exclusively dominated by magnetic systems, will be fundamentally boosted if optical drives and media are subject to uniform standards and become fully compatible, and multiuser drives are offered which enable the user to employ alternatively CD-ROM and EOD disks, and maybe WORM disks as well (and CD-R disks, respectively). A prerequisite, however, will be whether rewritable optical memories will use the MOR or the PCR process. This accord especially will be hard to reach. 

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