Effects of underlayer grain size on the microstructure of the magnetic layer in CoCrPt media

The average grain size of the CrTi or CrTiB underlayer was reduced from 16 to 7 nm and structural changes of the CoCrPt magnetic layer deposited on them were investigated. Reduction of the underlayer grain size tends to suppress the formation of bi-crystal clusters, though the magnetic layer has a CoCrPt (11.0) crystallographic texture. The average grain size of the magnetic layer showed a minimum when that of the underlayer was 9 nm. Further reduction of the underlayer grain size to 7 nm increased the average magnetic grain size about 15%. On the other hand, when the average underlayer grain size was less than 11 nm, the normalized standard deviation of the magnetic layer remained the same upon further reduction in the normalized standard deviation of the underlayer.