On design of Co-Cr perpendicular recording media for usage of a ring-type head

Co-Cr double-layer media were studied in order to improve perpendicular magnetic recording by using a ring-type head. A very thin semihard back layer (only 100 Å) with a high saturation moment showed a dramatic increase of reproducing output over a wide density region, while the recording sensitivity was also improved. The reproduced waveform with a sharp single peak desirable for actual systems occurs with peak shift as small as that for a single-layer Co-Cr medium. It is supposed that these improvements are caused by reduced demagnetization in the recording process. Design concepts of the media are discussed