Spintronics as a Classical Electron Device Paradigm for Information Processing

Electron devices, whether it is a transistor, traveling wave tube or an antenna, usually exploit the charge degree of freedom of electrons to elicit device functionality. An electron, however, has other degrees of freedom, such as its quantum mechanical “spin” that can be harnessed to implement either analog or digital devices. Sometimes the spintronic versions can be more energy-efficient than their counterparts based on charge. At other times, spin may be able to augment the role of charge to improve device performance or enable new and unusual functionalities. However, spin-based devices are not a panacea and there are vexing issues of reliability, difficulty with reading and writing of data, and occasionally the need for cryogenic operation. Spintronic logic gates, fashioned out of either single devices or many interacting devices, have also been frequently proposed over the last two decades, but never adopted in mainstream information processors because of their shortcomings and/or flaws. This review presents a brief survey of spin based <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">classical</i> electron devices and circuits for information processing. To keep it tractable, we avoid any reference to the fields where an electron’s spin (or an assembly of spin) is used to: (1) store (as opposed to process) information, i.e. memory; (2) encode a qubit for quantum information, (3) encode a p-bit for probabilistic computing and (4) communicate information over long distances (e.g. spintronic antennas). These fields deserve their own reviews.