Low noise mechanism in exchange coupled perpendicular recording media

Perpendicular magnetic recording is one of the most promising systems for ultra-high density recording beyond 200 Gbit/in/sup 2/. Steeper M-H loop slopes of the recording media are indispensable for obtaining a high recording resolution. Introduction of exchange coupling between the adjacent grains in the media is also effective in increasing the loop slope. However, increased exchange coupling generally causes enhanced medium noise due to increased magnetic domain size in the media. On the other hand, the dominant medium noise in double layered perpendicular recording media is the transition noise caused by jitter at the transitions. In this case, the noise could be small when a sharp transition is formed. Therefore, it would be possible to realize low noise media with a high resolution in perpendicular recording media. The low noise mechanism was studied using a simulation analysis.