By
combining two frontier technologies, spintronics and straintronics, a
team of researchers from Virginia Commonwealth University has devised
perhaps the world’s most miserly integrated circuit.
Their
proposed design runs on so little energy that batteries are not even
necessary; it could run merely by tapping the ambient energy from the
environment. Rather than the traditional charge-based electronic
switches that encode the basic 0s and 1s of computer lingo, spintronics
harnesses the natural spin?either up or down?of electrons to store bits
of data. Spin one way and you get a 0; switch the spin the other
way?typically by applying a magnetic field or by a spin-polarized
current pulse?and you get a 1.
During
switching, spintronics uses considerably less energy than charge-based
electronics. However, when ramped up to usable processing speeds, much
of that energy savings is lost in the mechanism through which the energy
from the outside world is transferred to the magnet.
The solution, as proposed in the AIP’s journal Applied Physics Letters, is to use a special class of composite structure called multiferroics.
These
composite structures consist of a layer of piezoelectric material with
intimate contact to a magnetostrictive nanomagnet (one that changes
shape in response to strain). When a tiny voltage is applied across the
structure, it generates strain in the piezoelectric layer, which is then
transferred to the magnetostrictive layer. This strain rotates the
direction of magnetism, achieving the flip. With the proper choice of
materials, the energy dissipated can be as low as 0.4 attojoules, or
about a billionth of a billionth of a joule.
This
proposed design would create an extremely low-power, yet high-density,
non-volatile magnetic logic and memory system. The processors would be
well suited for implantable medical devices and could run on energy
harvested from the patient’s body motion. They also could be
incorporated into buoy-mounted computers that would harvest energy from
sea waves, among other intriguing possibilities.
SOURCE: American Institute of Physics
