In BPMR, the recording physics is fundamentally different from conventional PMR and the write and read scheme must be totally reestablished[11],[14].Amajordisadvantageistheneed for write synchronization in which write field must be timed to coincide with the locations of patterned islands. The writing process in BPMR requires that the total switching field distribution, including various interference fields, must be less than the product of the head field gradient and the bit length to attain a high areal density [15]. An areal density beyond 5 Tb/in will be possible by BPMR with pattern fabrication- and write synchronization- tolerance, and , of much less than 1 nm, very narrow switching field distribution, very small interaction field, and a very narrow track writing system with high write field and field gradient. Advanced ECC-like BPM could improve design margin. A feasibility study [4], for example, showed that the head field gradient needs to be at least 500Oe/nmandtheswitchingfielddistributionshouldbetighter than 500 Oe (1-sigma) to achieve an areal density higher than about 4 Tb/in as shown in Fig. 3. Here, is the recording layer thickness.