"The magnets themselves are the built-in memory," Lambson said. "The real challenge is getting the wires and transistors working."
Lambson showed through calculations and computer simulations that a simple memory operation erasing a magnetic bit, an operation often called "restore to one" can be conducted with an energy dissipation very close, if not identical to, the Landauer limit.
He subsequently analyzed a simple magnetic logical operation. The first successful demonstration of a logical operation using magnetic nanoparticles was achieved by researchers at the University of Notre Dame in 2006. In that case, they built a three-input majority logic gate using 16 coupled nanomagnets. Lambson calculated that a computation with such a circuit would also dissipate energy at the Landauer limit.
Because the Landauer limit is proportional to temperature, circuits cooled to low temperatures would be even more efficient.
At the moment, electrical currents are used to generate a magnetic field to erase or flip the polarity of nanomagnets, which dissipates a lot of energy. Ideally, new materials will make electrical currents unnecessary, except perhaps for relaying information from one chip to another.
"Then you can start thinking about operating these circuits at the upper efficiency limits," Lambson said.
"We are working now with collaborators to figure out a way to put that energy in without using a magnetic field, which is very hard to do efficiently," Bokor said. "A multiferroic material, for example, may be able to control magnetism directly with a voltage rather than an external magnetic field."
Other obstacles remain as well. For example, as researchers push the power consumption down, devices become more susceptible to random fluctuations from thermal effects, stray electromagnetic fields and other kinds of noise.
"The magnetic technology we are
|Contact: Robert Sanders|
University of California - Berkeley