Composite perpendicular recording medium consisting of CoCrPt with large H-k perpendicular to 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 o n the medium thickness, a perpendicular medium with a large anisotropy fiel d, H-k perpendicular to Or (H-k perpendicular to-4 pi M-s), of over 10 or 5 kOe, respectively, is needed to obtain large output acid high resolution. Exploiting this large anisotropy field, a composite perpendicular medium wi th a (Co72Cr28)(78)Pt-22 layer over a Cr-rich Co72Cr28 layer was fabricated . By taking advantage of both the large anisotropy in the upper layer and t he strong particle interaction in the lower layer, the composite medium wit h a merged MR head obtained an S/N of 24.0 dB at 200 kFCI and a D-50 Of 205 kFCI, with a 50-nm magnetic spacing.