Straintronics: Digital and Analog Electronics With Strain-Switched Nanomagnets

The search for a binary switch that is more energy-efficient than a transistor has led to many ideas, notable among which is the notion of using a nanomagnet with two stable magnetization orientations that will encode the binary bits 0 and 1. The nanomagnet is switched between them with electrically generated mechanical strain. A tiny amount of voltage is required for switching, with energy dissipation on the order of a few to few tens of aJ. Logic gates and memory, predicated on this technology, have been demonstrated in our group. While they indeed dissipate very little energy, they are unfortunately plagued by unacceptably high switching error probability that hinders their application in most types of Boolean logic. Fortunately, they can still be used in applications that are more forgiving of switching errors, e.g. probabilistic computing, analog arithmetic circuits, belief networks, artificial neurons, restricted Boltzmann machines, image processing, and others where the collective activity of many devices acting cooperatively elicit the computing or signal processing function and the failure of a single or few devices does not matter critically. These ultra-energy-efficient strain-switched nanomagnets can also be used for non-computing devices such as microwave oscillators that perform better than spin-torque-nano-oscillators. This short review provides an introduction to this exciting burgeoning field.