Do you wish your computer was faster? Engineers and physicists from Germany have demonstrated the quickest prototype yet of an advanced form of RAM tipped by hardware manufacturers to be the future of computing. The device is so fast it brushes against a fundamental speed-limit for the process.

Magnetoresistive random access memory (MRAM) is a faster and more energy efficient version of the RAM used in computers today, and hardware companies think it will in a few years dominate the market. Its speed and low power will in particular boost mobile computing.

Whereas conventional RAM stores a digital 1 or 0 as the level of charge in the capacitor, MRAM stores it by changing the north-south direction of a tiny magnet's magnetic field. Each variable magnet is positioned next to one with a fixed field. Reading a stored value involves running a current through the pair to discover the direction of the variable magnet's field.

Spin flips

The MRAM that IBM and most other manufacturers are betting on uses the spins of electrons to flip the magnetic fields, called spin-torque MRAM.

Now 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.

Wobble control

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.

Robert Buhrman, an expert in nanomagnetics at Cornell University, New York, is impressed but notes that a full MRAM device has not yet been made.

The current used by the German device is at present too electrically dense to be supplied by the transistors used in MRAM circuits. "The next thing that needs to be done is to get the switching currents down to a scale that is compatible with the [standard] CMOS (complementary metal–oxide–semiconductor) transistor," said Buhrman.

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