The new research shows that they do. It took about 10 nanoseconds, and a distance of a micron, for a domain wall to reach its final velocity, about 140 meters per second. It took another 10 nanoseconds, and one micron, for the domain wall to slow to a stop after the current was turned off. Thus domain walls do indeed behave like particles with mass, and move in a predictable way.
The researchers were careful to use electrical pulses that were just a few nanoseconds in length. If they had used pulses whose duration was similar to the time it takes the domain wall to reach its final velocity, then the acceleration of the domain wall wouldn’t have been measurable.
“It is extremely important to account for these effects in clocking schemes of racetrack memory,” says Shan Wang, professor of materials science and engineering and electrical engineering at Stanford, referring to the algorithms that would control the reading and writing of bits in a racetrack memory device. “Otherwise, domain walls … would be written in wrong locations of the nanowire.”
However, Wang says a practical racetrack memory device remains some way off. “This paper only shows the exquisite shifting of bits, but it is not a memory device yet.”
Still to be determined, for instance, says Peter Fischer, a staff scientist at Lawrence Berkeley National Labs, is “how clean and perfect the device needs to be to work billions of times.”
Parkin says racetrack memory’s reliability is likely to depend on the materials used for the nanowires, and the design—which will be worked out as a prototype is developed. “It shouldn’t take too long,” Parkin says. “Maybe in two years we should have this prototype.”