Today, Hitachi GST's Travelstar drives have areal densities which are up to seventy gigabits per square inch (Travelstar 5K80). If conventional disk media were used at this areal density, the effects of supermagnetism could reduce the thermal stability of magnetically stored information. To delay this effect, Hitachi GST pioneered the use of AFC media and previously introduced this media into the Travelstar series in 2001 and into other disk drive products after that. Hitachi GST also pioneered the use of exchange coupled structures and materials that are used in today's GMR heads. The AFC media structure consists of two magnetic layers separated by a thin, 6 Å, film of the element ruthenium. This film produces an antiferromagnetic coupling of top and bottom layers. The ruthenium film is only about 3 atom layers in thickness permitting the effective magnetic thickness, Mrt, of this entire structure to be the difference between top and bottom magnetic films, and therefore independent of the actual individual layer thicknesses. Both magnetic layers can now be thicker at higher areal densities allowing larger alloy grains which are more thermally stable. AFC media is expected to extend areal densitiesgrowth to 100 Gbits/in2 and beyond while maintaining good thermal stability of the recorded information.