For more than 40 years, magnetic recording has been the dominant technology for electronic data storage. During this time, the areal storage density on disks has risen to >108 bits/cm2. On tapes the corresponding figure is 0.2 × 108 bits/cm2. Thus each bit uses about a 1.0 μm2 area. These 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. All this is accomplished at head-disk spacings of ≈0.2 μm 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 well 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 present dominant position in the foreseeable future. The answer is — “Very likely, yes” — but this prediction is based on the assumption that a number of formidable fascinating problems will be solved in order to increase the areal bit density.

The five articles in this special issue present 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.