Magnetic Recording Materials: Present and Future
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For more than 40 years, magnetic recording has been the dominant technology for electronic data storage. During this rime, the areal storage density on disks has risen to >108 bits/cm2. On tapes the corresponding figure is 0.2 x 108 bits/cm2. Thus each bit uses about a 1.0 /nm2 area. Thèse bits are written and read at data rates that require head-disk relative speeds of tens of meters per second and head-tape relative speeds of several meters per second. AU this is accomplished at head-disk spacings of =0.2 nm and with contact recording for tapes. It is truly a wonder that the Systems work as well as they do. In fact, for many features in magnetic recording Systems it isn't certain why they work as weU as they do. However, the demand for storage capacity is estimated to be increasing at about 40% per year. So it is natural to ask whether magnetic recording can maintain its présent dominant position in the foreseeable future. The answer is — "Very likely, yes" — but this prédiction is based on the assumption that a number of formidable fascinating problems will be solved in order to increase the areal bit density.
Ami Berkowitz MRS BULLETIN/MARCH1990
The five articles in this spécial issue présent the state-of-the-art in those key areas of magnetic recording that involve materials science, and they define the problems involved in increasing storage density. James U. Lemke discusses the background and outlook for magnetic recording. Tomasz Jagielinski considers recording heads. The tribological issues of lubrication and overcoats are presented by A.M. Homola, CM. Mate, and G.B. Street. Particulate média are covered by M. P. Sharrock, while thin film média are described by Jack H. Judy.
Future magnetic recording Systems will utilize materials engineered on the nanometer scale. In ail of thèse areas, the dimensional unit of interest is rapidly becoming the
Andrew M. Homola
nanometer. This is due in part, of course, to the shrinking dimensions of the various components of recording Systems. Another reason is that the structural and magnetic properties of surfaces and interfaces are increasingly occupying the attention of investigators in magnetic recording. Every one of the présent électron, photon, neutron, and tunneling surface characterization techniques are employed. The object is more than understanding and controlling surface behavior. Magnetic recording Systems of the future wiïl utilize materials engineering in the true sensé of the term — namely, manipulating surface and interfacial features to create magnetic properties that are simply not available in equilibrium Systems. Particulate média hâve long benefited from this approach; the particles in videotapes are surface treated with cobalt to increase coercive force. Sputtered film média already rely on interactions with appropriate underlayers to achieve control of grain size and orientation. The dimensional considérations and interfacial interactions are perhaps most dramatically demonstrated by the thickness of the lubricant that protects disks rotating
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