Keeping Track: Vertically oriented nanowires (top left, middle) illustrate how electric current is used to slide tiny magnetic patterns around the nanowire “racetrack” where a device can read and write data. A device reads data from the stored pattern (top right) by measuring the magnetoresistance of the patterns. Writing data (the two images below the read head) can be done by applying an electrical current to a second nanowire at a right angle to the data-storing wire. It is possible to fabricate the nanowires in a vertical array (middle right) and horizontally (bottom two images).
“This is the first time that someone has demonstrated that you can move two or three of these domain walls without upsetting them or causing them to interfere,” Parkin says. Parkin notes that it could take four years before he has a racetrack memory prototype, and three more years to commercialize it.
The appeal of racetrack memory, says Igor Zutic, professor of physics at the State University of New York at Buffalo, is that it can “unify the best properties of inexpensive, high-density storage of magnetic hard drives with high-speed operation of random-access memory in a single device, while avoiding their main shortfalls, such as speed and cost, respectively.”
The next step, Parkin says, is to implement a device to read the bits of data. He suspects that this will be fairly straightforward, because he could use pre-existing technology. In 2004, Parkin developed the small magnetic device that reads data from magnetic disk drives, and these devices, called magnetic tunnel junctions, would be sensitive enough to read the tiny magnetic fields produced by the domain walls in the nanowires.