CoCrPtTa and Co/Pd perpendicular magnetic recording media with amorphous underlayers

The effect of amorphous carbon underlayers on magnetic properties and read-write characteristics of Co/sub 73/Cr/sub 18/Pt/sub 6/Ta/sub 3/ single layer and Co/Pd multilayer perpendicular magnetic recording media were investigated. The increase in H/sub c/ and decrease in /spl alpha/, defined as 4/spl pi/(dM/dH)/sub H=Hc/, were observed by increasing the underlayer thickness for both Co/sub 73/Cr/sub 18/Pt/sub 6/Ta/sub 3/ and Co/Pd media. The media with a low /spl alpha/ value, suggesting a decrease in the exchange coupling, exhibited the higher coercivity and the improvement of S/N ratio. In read-write experiments, the improvement of S/N ratio for the Co/Pd media was achieved up to 400 kFRPI or even higher in the recording density by increasing carbon underlayer thickness, while that for the Co/sub 73/Cr/sub 18/Pt/sub 6/Ta/sub 3/ media was obtained up to ca. 250 kFRPI.