Enhancement of exchange coupling for antiferromagnetically coupled media

Antiferromagnetically coupled (AFC) media with CoPt or Co interlayers inserted between a Ru layer and CoCrPtB magnetic layers were prepared in order to enhance the exchange coupling and the thermal stability. The exchange coupling field Hex increased from 0.6 to 4.2 kOe by increasing the thickness of the Co interlayer from 0 to 1 nm. The coupling energy J increases with increasing thickness of the interlayer. The coupling energy J of the AFC media with the interlayer are ten times larger (for 1-nm-thick Co interlayer) and five times larger (for 1-nm-thick CoPt interlayer) than that of the medium without the interlayer. Thermal stability factor KuV/kBT for the media with 1-nm-thick Co and 1-nm-thick CoPt interlayers are about 10% larger than that for the medium without the interlayer. The results suggest that the enhancement of the exchange coupling energy induces the increasing of KuV/kBT in the AFC media.