19 Nisan 2008 Cumartesi

Racetrack Memory

Racetrack Memory is an experimental non-volatile memory device under development at IBM's Almaden Research Center by a team led by Stuart Parkin, as well as teams at various other locations. In early 2008 a 3-bit version was successfully demonstrated.

IBM's version of racetrack uses spin-coherent electric current to move the magnetic domains along an U-shaped nanoscopic wire. As current is passing through the wire, the domains move over the magnetic read/write heads positioned at the bottom of the U, which alter the domains to record patterns of bits. A memory device is made up of many such wires and read/write elements. In general operational concept, racetrack memory is similar to the earlier twistor memory or bubble memory of the 1960s and 70s, but uses much smaller magnetic domains and dramatic improvements in magnetic detection capabilities to provide far higher areal densities.

One limitation of the early experimental devices was that the magnetic domains could only be pushed slowly through the wires, requiring current pulses on the orders of microseconds to move them successfully. This was unexpected, and led to performance roughly equal to hard drives, as much as 1000 times slower than predicted. Recent research at the University of Hamburg has traced this problem to microscopic imperfections in the crystal structure of the wires which led to the domains becoming "stuck" at these imperfections. Using an x-ray microscope to directly image the boundaries between the domains, their research found that domain walls would be moved by pulses as short as a few nanoseconds when these imperfections were absent. This corresponds to a macroscopic speed of about 110 m/s.

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