Extremely high-density longitudinal magnetic recording media

Areal density progress in magnetic recording is largely determined by the a bility to fabricate low-noise, granular thin Im media with sufcient stabili ty against thermal agitation to warrant long-term data storage. A key requi rement is a medium microstructure with small, magnetically isolated grains to establish optimal macro- and micro-magnetic properties. A lower bound fo r the minimal average grain diameter, compatible with thermal stability, is imposed by the write eld capability of the recording head. It is 10-12nm a ssuming maximal writeable coercivities of 400 kA/m (5000 Oe). These are alr eady achieved in today's state-of-the-art CoCr-based thin lm alloy media, l eaving little room for further improvements and density gains based on cont inued grain size reduction. A threefold reduction in grain diameter, howeve r, translating into a tenfold increase in areal density is theoretically po ssible if write eld constraints can be overcome, allowing utilization of ma gnetically harder alloys. This review emphasizes materials and fabrication aspects behind media for extremely high-density longitudinal magnetic recor ding. Special attention is paid to thermal stability and write coercivity c onstraints. Various alternative media designs for extremely high-density re cording beyond 40-100Gbits/inch(2) are reviewed.