John S. Best

The future of magnetic data storage technology

In this paper, we review the evolutionary path of magnetic data storage and examine the physical phenomena that will prevent us from continuing the use of those scaling processes which have served us in the past. It is concluded that the first problem will arise from the storage medium, whose grain size cannot be scaled much below a diameter of ten nanometers without thermal self-erasure. Other problems will involve head-to-disk spacings that approach atomic dimensions, and switching-speed limitations in the head and medium. It is likely that the rate of progress in areal density will decrease substantially as we develop drives with ten to a hundred times current areal densities. Beyond that, the future of magnetic storage technology is unclear. However, there are no alternative technologies which show promise for replacing hard disk storage in the next ten years.

Direct measurement of recording head fields using a high‐resolution inductive loop (invited)

A method is described for direct measurement of the magnetic microfield from a recording head. The method employs a thin film ‘‘microloop’’ as a transducer which by induction senses the recording head field. Measurements are presented on both a thin film and a ferrite head. Fits to the data allow the absolute efficiency to be determined. Data on the frequency dependence of head efficiency are also presented.

Measurements of surface magnetic fields in contact perpendicular recording using a high‐resolution magnetoresistive transducer

A high‐resolution vertical magnetoresistive transducer has been used to measure the magnetic field at the surface of rigid CoCr(Ta)/NiFe perpendicular recording media. Very sharp magnetic transitions achieved by contact recording were observed at the edges of the main pole of a single‐sided main‐pole‐driven perpendicular head, both along and across the recording track, with transition widths (10–90%) of 240 and 390 nm, respectively.