Ion beam modification of exchange coupling to fabricate patterned media

For bit-patterned media, media with low remanent magnetization (M(r)) and high M(r) regions are needed for storing information, which is usually achieved by lithographically defining magnetic and non-magnetic regions. In this work, we have investigated the use of ion beam modification of media surface to define the low and high M(r) states using a medium that is at a low M(r) state to start with. The low M(r) state is achieved by the use of synthetic antiferromagnetic coupling obtained in Co-alloy/Ru/Co-alloy trilayer structured film. Local ion beam modification at 30 keV energy using Ga+ ions was used to create high M(r) regions. AFM and MFM observations indicated that patterned regions of low and high M(r) can be observed with ion beam irradiation. This technique is a potential method to achieve patterned media without the need of planarization techniques.