Electroless plated Co-Ni-Re-P alloy films for use as perpendicular magnetic recording media were studied. It was found that the addition of tartronic acid to the plating bath makes it possible to form Co-Ni-Re-P perpendicular anisotropic films with no MnSO4 present. Co-Ni-Re-P alloy films, with a composition simpler than that of previously developed Co-Ni-Re-Mn-P films, has a greater potential than do the latter for practical use as perpendicular recording media. The read/write characteristics of 8-inch disks employing Co-Ni-Re-P films were also measured, in combination with a ring head. Characteristics almost equal to those of media containing Mn were obtained, and even higher recording densities are expected, given improved matching of head and disk properties. A recording density of D50 = 54 kFRPI was obtained for a 0.2 micron thick medium, using a 0.33 micron gap ring head and with a 0.12 micron head-medium spacing.
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