Researchers in Germany have built a spin-torque system that is dramatically faster than any other. Santiago Serrano-Guisan and Hans Schumacher of the Physical-Technical Federal Laboratory of Germany worked with University of Bielefeld and Singulus Nano-Deposition Technologies researchers to build it from tiny pillars 165 nanometres tall.
The top end of each pillar acts as a variable magnet that stores data, whereas the bottom ends are fixed magnets. A current passing through a pillar from bottom to top has the spin of its electrons lined up by the permanent-magnet region. When those electrons reach the pillars' other end, they flip the variable magnet region's field to match. The field can be flipped back by reversing the current.
Usually when the field is flipped it takes some time to settle into its new orientation. The north-south axis draws a few circles in the air before settling into place. But theoretical work says it needs to draw only one circle before finding its new position, making the process faster. The German team achieved that, developing a way to observe and control the field’s wobble during and after the flip.
By adjusting the duration and strength of the electrical pulse that flips the field, only a single "wobble" is allowed to take place, matching the theoretical limit. The result is a device many times faster than any before. "Present MRAM are programmed by pulses of about 10 nanoseconds duration," said Serrano-Guisan. "So we are ten times faster." The very best conventional RAM needs around 30 nanoseconds for an equivalent operation.