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 journalApplied Physics Letters, is to use a special class of composite structure called multiferroics.
These composite structures consist of a layer of piezo-electric 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 piezo-electric 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.
The article, titled "Hybrid spintronics and straintronics: A magnetic technology for ultra-low-energy computing signal processing" is published inApplied Physics Letters. The authors are Kuntal Roy, Supriyo Bandyopadhyay, and Jayasimha Atulasimha.