Composite perpendicular recording medium consisting of CoCrPt with large H/sub k/spl perp// and CoCr with positive inter-particle interaction

The demagnetizing field near the top surface of a medium for perpendicular recording is compared with that of a medium for longitudinal recording. On the basis of both the result of this comparison and the output dependence on the medium thickness, a perpendicular medium with a large anisotropy field, H/sub k/spl perp// or (H/sub k/spl perp//-4/spl pi/M/sub s/), of over 10 or 5 kOe, respectively, is needed to obtain large output and high resolution. Exploiting this large anisotropy field, a composite perpendicular medium with a (Co/sub 72/Cr/sub 28/)/sub 78/Pt/sub 22/ layer over a Cr-rich Co/sub 72/Cr/sub 28/ layer was fabricated. By taking advantage of both the large anisotropy in the upper layer and the strong particle interaction in the lower layer, the composite medium with a merged MR head obtained an S/N of 24.0 dB at 200 kFCI and a D/sub 50/ of 205 kFCI, with a 50-nm magnetic spacing.