Researchers at IBM's Almaden Research Center recently demonstrated the underlying technology for 'racetrack memory,' which they contend will eventually replace flash memory and hard drives. Spintronics is a new field of engineering which stores and controls electron spin flow, instead of storing and controlling electrical charge. Bits are 'generated by the magnetic spin of electrons rather than their charge.' Almaden's proof-of-concept shift register prototype encodes bits into magnetic domain walls on a silicon high-aspect-ratio nanowire, or 'racetrack,' of any length. Current-controlled 'mass-less motion,' or spin-polarized current pulses, moves the domain walls along the nanowire to retrieve and store information, which isn't possible with magnetic fields. IBM first generation racetrack will use an area of silicon one micron wide by 10 microns high and store 10 bits, replacing flash memory. As soon as 100 bits can be stored in the same area, hard-disk drives can be replaced. In 1989, IBM fellow Stuart Parkin invented a spin valve sensing device which increased disk drive capacity a thousand-fold. Next, his group invented its magnetic tunnel junction (MTJ) that separates two magnetic layers with a dielectric, and built its first magnetic RAMs in 1999. Nowadays, Parkin estimates an iPod using racetrack memory could store 100 times more data than existing models. Next, a fast MTJ read head is needed at the top of each racetrack. The prototype has its racetrack running parallel to the silicon chip's surface, but IBM plans to sink vertical nanowires into silicon.