Hitatchi aims for 4TB HDD’s in 2011
The CPP-GMR drive essentially changes the structure of drive heads. Current drives come with a tunnel magnetoresistance head. In these, an insulating layer sits between two magnetic layers. Electrons can tunnel through the layer. Precisely controlling the tunneling ultimately results in the 1s and 0s of data. Unfortunately, drive heads need to be shrunk as areal density, the measure of the amount of data that can be squeezed onto a square inch of media, increases. Shrinking the heads increases electrical resistance, which in turn creates electrical noise and potential degradation in performance. Past 500 gigabits per square inch of areal density, TMR heads may not work reliably (Current top-end drives exhibit an areal density of around 200 gigabits per square inch.) In a CPP-GMR head, the insulator is eliminated and replaced by a conductor, usually copper. Instead of running parallel with the middle layer, the current runs at a perpendicular angle. The structure reduces resistance and thus allows the head to be shrunk.