Supriyo Bandyopadhyay - Magnetic Straintronics: An Energy-Efficient Hardware Paradigm for Digital and Analog Information Processing

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This monograph introduces the readers to some of the most important topical areas of magnetic straintronics that could lead to a potent hardware platform for processing digital and analog information at a minimal energy cost. Magnetic straintronics, hereafter referred to simply as straintronics for the sake of brevity, is the rapidly burgeoning field of science and engineering dealing with manipulating the magnetic states of magnetostrictive nanomagnets with electrically generated mechanical strain. These nanomagnets can implement a wide range of functional devices and circuits that are extremely energy-efficient and hence ideal for many applications, such as embedded processors, medically implanted devices, aggressively miniaturized stealth devices for defense and crime-fighting, and even mainframe computers.

The primitive unit of all digital hardware (computers, signal processors, communication devices, etc.) is a binary switch that has two states encoding the binary bits 0 and 1. Digital computing and signal processing are carried out by switching between the two states. The best switch is the one that can switch the fastest with minimal energy dissipation while boasting a low switching error rate for reliability. A straintronic switch, fashioned out of a magnetostrictive nanomagnet whose magnetization can assume only two stable orientations (representing bits 0 and 1), may be able to switch in less than 1 ns with energy dissipation as low as ~1 aJ when the magnetization is switched with electrically generated mechanical strain. The associated energy-delay product is one order of magnitude lower than what the best silicon field effect transistors today can offer. The low energy-delay product, of course, comes at a cost, and the cost is usually a high switching error rate. That high rate is a serious disadvantage for some applications, such as Boolean logic, but not so much for collective computational models (e.g. neuromorphic networks) where the collective activities of many devices working cooperatively elicit the computational or signal processing activity, and the failure of one or few devices to act properly does not impair the circuit operation. Straintronic devices have other attractive attributes as well, such as unusual characteristics that can be exploited to build better circuits, and, of course, non-volatility, which can be leveraged to implement superior architectures for specific digital and analog circuits. Non-volatility implies that the information in the switches (i.e. which of the two states it is in) is not lost once the device is powered off. Non-volatility can offer other advantages as well, such as resilience to hacking, energy saving (accruing from the fact that data do not have to be refreshed periodically), and no boot delay when powering up a computer.

This monograph mostly (but not exclusively) presents research carried out in the authors group and in the groups of his collaborators in the area of magnetic straintronics. The author acknowledges all his students who have worked in the field (too many to name individually) and his collaborators who (in alphabetical order) are Profs. Jayasimha Atulasimha, Anjan Barman, Avik W. Ghosh, Bin Ma, Csaba Andras Moritz, Erdem Topsakal, Amit Ranjan Trivedi and Jian-ping Wang.

Comments on this work are welcome and can be emailed to the author at sbandy@vcu.edu.

The two most important infrastructures in our society are energy and information because they define our civilizations level of technical advancement. The Kardashev scale [].