Supriyo Bandyopadhyay, Ph.D. profile photo

Supriyo Bandyopadhyay, Ph.D.

Commonwealth Professor, Department of Electrical and Computer Engineering

Engineering West Hall, Room 238, Richmond, VA, United-States

(804) 827-6275

Professor Bandyopadhyay has authored and co-authored nearly 400 research publications


Image for publication on Nanomagnetic and Spintronic Devices for Energy-Efficient Memory and ComputingImage for publication on Introduction to Spintronics, Second EditionImage for publication on Physics of Nanostructured Solid State DevicesImage for publication on Problem Solving in Quantum Mechanics: From Basics to Real-World Applications for Materials Scientists, Applied Physicists and Devices EngineersImage for publication on Contemporary Topics in Semiconductor SpintronicsImage for publication on Quantum Dots and Nanowires



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Supriyo Bandyopadhyay is Commonwealth Professor of Electrical and Computer Engineering at Virginia Commonwealth University. He received a B. Tech degree in Electronics and Electrical Communications Engineering from the Indian Institute of Technology, Kharagpur, India; an M.S degree in Electrical Engineering from Southern Illinois University, Carbondale, Illinois; and a Ph.D. degree in Electrical Engineering from Purdue University, West Lafayette, Indiana. He spent one year as a Visiting Assistant Professor at Purdue University, West Lafayette, Indiana (1986-87) and then nine years on the faculty of University of Notre Dame. In 1996, he joined University of Nebraska-Lincoln as Professor of Electrical Engineering, and then in 2001, moved to Virginia Commonwealth University as a Professor of Electrical and Computer Engineering, with a courtesy appointment as Professor of Physics. He directs the Quantum Device Laboratory in the Department of Electrical and Computer Engineering. Research in the laboratory has been frequently featured in national and international media. Its educational activities were highlighted in a pilot study conducted by the ASME to assess nanotechnology pipeline challenges. The laboratory has graduated many outstanding researchers who have won numerous national and international awards.

Prof. Bandyopadhyay has authored and co-authored nearly 400 research publications and presented nearly 150 invited or keynote talks at conferences and colloquia/seminars across four continents. He is the author of three popular textbooks, including the only English language textbook on spintronics. He is currently a member of the editorial boards of eleven international journals and served in the editorial boards of four other journals in the past. He has served in various committees of over 70 international conferences and workshops. He is the founding Chair of the Institute of Electrical and Electronics Engineers (IEEE) Technical Committee on Spintronics (Nanotechnology Council), and past-chair of the Technical Committee on Compound Semiconductor Devices and Circuits (Electron Device Society). He was an IEEE Electron Device Society Distinguished Lecturer (2005-2012) and is currently an IEEE Nanotechnology Council Distinguished Lecturer. He is also a past Vice President of the IEEE Nanotechnology Council. Prof. Bandyopadhyay is the winner of many awards and distinctions.

Industry Expertise

  • Education/Learning
  • Research

Areas of Expertise

Self-assembly of Regimented Nanostructure ArraysSpintronicsQuantum DevicesHot Carrier Transport in NanostructuresNanoelectronicsQuantum ComputingNanomagnetismComputing ParadigmsOptical Properties of NanostructuresCoherent spin transport in Nanowires for Sensing and Information ProcessingNanowire-based Room Temperature Infrared Detectors


University Award of Excellence | professional

Virginia Commonwealth University faculty award for performing in a superior manner in teaching, scholarly activity and service. One award is given in any year. It is one of the highest awards the University can bestow on a faculty member.


Virginia's Outstanding Scientist | professional

Named by the Governor of the State of Virginia, 2016. One of two recipients in the State of Virginia. This award is given across all fields of engineering, science, mathematics and medicine.


Electrical and Computer Engineering Lifetime Achievement Award, VCU | professional

School of Engineering, Virginia Commonwealth University, 2015. One of two such awards given in the department's history.

Distinguished Scholarship Award, Virginia Commonwealth University | professional

Virginia Commonwealth University, 2012. One award is given in any year and covers all fields of science, humanities, business, education, social science, engineering and medicine.


Interdisciplinary Research Award, University of Nebraska-Lincoln | professional

Given jointly by the College of Engineering, the College of Science, and the Institute for Agricultural and Natural Resources.


IBM Faculty Award | professional

International Business Machines, 1990


College of Engineering Service Award, University of Nebraska-Lincoln | professional

College of Engineering, University of Nebraska-Lincoln, 1999


College of Engineering Research Award, University of Nebraska-Lincoln | professional

College of Engineering, University of Nebraska Lincoln, 1998


Distinguished Alumnus Award, Indian Institute of Technology, Kharagpur, India | professional

One of seven industry, government and academic leaders worldwide honored with this award in 2016. All are alumni of Indian Institute of Technology, Kharagpur.


Fellow of the Institute of Electrical and Electronics Engineers (IEEE) | professional

Citation: For contributions to device applications of nanostructures


Fellow, American Physical Society | professional

Citation: For pioneering contributions to device applications of nanostructures.


Fellow of the Electrochemical Society | professional

In recognition of the contributions to the advancement of science and technology, for leadership in electrochemical and solid state science and technology and for active participation in the affairs of the Electrochemical Society


Fellow of the Institute of Physics | professional

For outstanding contributions to physics


Fellow of the American Association for the Advancment of Science | professional

For pioneering contributions to spintronics and device applications of self assembled nanostructures


State Council of Higher Education for Virginia (SCHEV) Outstanding Faculty Award | professional

The Outstanding Faculty Awards are the Commonwealth's highest honor for faculty at Virginia's public and private colleges and universities. These awards recognize superior accomplishments in teaching, research, and public service.



Purdue University

Ph.D., Electrical Engineering

Southern Illinois University

M.S., Electrical Engineering

Indian Institute of Technology, Kharagpur

B.Tech, Electronics and Electrical Communications Engineering


  • Institute of Electrical and Electronics Engineers : Vice President Nanotechnology Council Associate Editor IEEE Transactions on Electron Devices Technical Committee Chairs
  • Optical Society of America : Member of Technical Group on Photonic Detection
  • American Physical Society
  • The Electrochemical Society
  • American Association for the Advancement of Science
  • Institute of Physics (UK): Editorial Board Member of the Journal of Nanotechnology

Media Appearances

IIT-Kharagpur to confer Distinguished Alumnus Award at the 62nd convocation

Times of India  online


Kolkata: Indian Institute of Technology Kharagpur will confer the Distinguished Alumnus Award on the occasion of the 62nd convocation of the Institute which will be organized on July 30 and 31. Seven eminent alumni have been selected for the award for their exceptional professional achievements in the industry, in the academia or as entrepreneur. The awardees are - Dr Anurag Acharya, Ajit Jain, Asoke Deyasarkar, professor Gautam Biswas, professor Indranil Manna, professor Supriyo Bandopadhyay and Professor Venkatesan Thirumalai.

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Putting a New Spin on Electronics

Community Idea Stations  


An international leader in the field of spintronics, Dr. Supriyo Bandyopadhyay directs the Virginia Commonwealth University (VCU) Quantum Device Lab. He was recently named one of Virginia’s Outstanding Scientists by Gov. Terry McAuliffe and the Science Museum of Virginia. This is the first of several articles on all of the 2016 Virginia Outstanding STEM Award winners...

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EVMS diabetes researcher named one of two outstanding scientists of the year in Virginia

The Virginia Pilot  


The other is Dr. Supriyo Bandyopadhyay, a professor in the Department of Electrical and Computer Engineering at Virginia Commonwealth University. His work entails making electronic gadgets out of tiny magnets 1,000 times smaller than the thickness of a human hair. The magnets consume so little energy that they can work without a battery by harvesting energy from wireless networks and wind vibrations...

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Single-electron devices come together



Back in the 1990s, Supriyo Bandyopadhyay, Biswajit Das and Albert Miller at the University of Notre-Dame in France described how to inscribe and manipulate ‘bits’ of logic information in the spin of single electrons. Among the advantages of this computing architecture, they list speed, information density, robustness and power efficiencies. Other groups have also studied how control of single electrons may benefit quantum computing...

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Straintronic spin neuron may greatly improve neural computing

ECN Magazine  online


"Most computers are digital in nature and process information using Boolean logic," Bandyopadhyay told "However, there are certain computational tasks that are better suited for 'neuromorphic computing,' which is based on how the human brain perceives and processes information. This inspired the field of artificial neural networks, which made great progress in the last century but was ultimately stymied by a hardware impasse. The electronics used to implement artificial neurons and synapses employ transistors and operational amplifiers, which dissipate enormous amounts of energy in the form of heat and consume large amounts of space on a chip. These drawbacks make thermal management on the chip extremely difficult and neuromorphic computing less attractive than it should be."

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'Straintronic spin neuron' may greatly improve neural computing  online


Researchers have proposed a new type of artificial neuron called a "straintronic spin neuron" that could serve as the basic unit of artificial neural networks—systems modeled on human brains that have the ability to compute, learn, and adapt. Compared to previous designs, the new artificial neuron is potentially orders of magnitude more energy-efficient, more robust against thermal degradation, and fires at a faster rate. The researchers, Ayan K. Biswas, Professor Jayasimha Atulasimha, and Professor Supriyo Bandyopadhyay at Virginia Commonwealth University in Richmond, have published a paper on the straintronic spin neuron in a recent issue of Nanotechnology.

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Non-volatile memory improves energy efficiency by two orders of magnitude  online


By using voltage-generated stress to switch between two magnetic states, researchers have designed a new non-volatile memory with extremely high energy efficiency—about two orders of magnitude higher than that of the previous most efficient non-volatile memories. The engineers, Ayan K. Biswas, Professor Supriyo Bandyopadhyay, and Professor Jayasimha Atulasimha at Virginia Commonwealth University in Richmond, Virginia, have published their paper on the proposed non-volatile memory in a recent issue of Applied Physics Letters.

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Researchers to develop battery-less, energy-efficient CPUs

EET Asia  


"The purpose of this work is to establish a new paradigm for digital computing which will be extremely energy-efficient and hopefully allow us to pack more and more computing devices on a chip without having to worry about excessive heat generation," said Supriyo Bandyopadhyay, co-principal investigator for the study at VCU and professor of electrical and computer engineering in the VCU School of Engineering. "This will allow us to increase the computational prowess of computers beyond what is available today."...

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Researchers aim for energy-harvesting CPUs

EE Times  online


SAN FRANCISCO—A team of researchers from Virginia Commonwealth University (VCU) was awarded two grants totaling $1.75 million from the U.S. National Science Foundation and the Nanoelectronics Research Initiative of Semiconductor Research Corp. to create powerful, energy-efficient computer processors that can run an embedded system without requiring battery power. The research, based on a paper published by the VCU research team in the August issue of the journal Applied Physics Letters, replaces transistors with special tiny nanomagnets that can also process digital information, theoretically reducing the heat dissipation by one 1,000 to 10,000 times, according to VCU.

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Hybrid spintronics and straintronics enable ultra-low-energy computing and signal processing

Kurzweil  online


Ref.: Kuntal Roy, Supriyo Bandyopadhyay, and Jayasimha Atulasimha, Hybrid spintronics and straintronics: A magnetic technology for ultra-low-energy computing signal processing, Applied Physics Letters, 2011; [DOI:10.1063/1.3624900]

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Strain and spin could drive ultralow energy computers

Institute of Physics: PhysicsWorld  online


Tiny layered magnets could be used as the basic processing units in highly energy-efficient computers. So say researchers in the US who have shown that the magnetization of these nanometre-sized magnets can be switched using extremely small voltages that induce mechanical strain in a layer of the material. The resulting mechanical deformations affect the behaviour of electron spins, allowing the materials to be used in spintronics devices. These are electronic circuits that exploit the spin of the electron as well as its charge. Hybrid spintronics/straintronics processors made from such magnets would require very little energy and therefore could work battery-free by harvesting energy from their environment. As a result they could find a host of unique applications, including implantable medical devices and autonomous sensors.

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Dr. Supriyo Bandyopadhyay: Spintronics Drives Next-Gen Computing

NanoScienceWorks  online


“Spin based computers can be powered by small lightweight batteries. I am particularly interested in organic spintronics. Organics can sustain spin memory for very long times and organics can be integrated with flexible substrates. One day that may lead to wearable spin based organic supercomputers housed in a wristwatch and powered by a wristwatch battery,” Dr. Bandyopadhyay told Dr. Bandyopadhyay also serves as Professor of Electrical Engineering and Professor of Physics at VCU.

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Spintronics: Making Computers Smaller and Faster

Science Daily  online


Researchers have made an important advance in the emerging field of 'spintronics' that may one day usher in a new generation of smaller, smarter, faster computers, sensors and other devices, according to findings reported in today's issue of the journal Nature Nanotechnology. The research field of 'spintronics' is concerned with using the 'spin' of an electron for storing, processing and communicating information. The research team of electrical and computer engineers from the Virginia Commonwealth University's School of Engineering and the University of Cincinnati examined the 'spin' of electrons in organic nanowires, which are ultra-small structures made from organic materials. These structures have a diameter of 50 nanometers, which is 2,000 times smaller than the width of a human hair. The spin of an electron is a property that makes the electron act like a tiny magnet. This property can be used to encode information in electronic circuits, computers, and virtually every other electronic gadget. "In order to store and process information, the spin of an electron must be relatively robust. The most important property that determines the robustness of spin is the so-called 'spin relaxation time,' which is the time it takes for the spin to 'relax.' When spin relaxes, the information encoded in it is lost. Therefore, we want the spin relaxation time to be as long as possible," said corresponding author Supriyo Bandyopadhyay, Ph.D., a professor in the Department of Electrical and Computer Engineering at the VCU School of Engineering.

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Spintronics, the Way to Faster and Smaller Computers

Softpedia News  online


"In order to store and process information, the spin of an electron must be relatively robust. The most important property that determines the robustness of spin is the so-called 'spin relaxation time,' which is the time it takes for the spin to 'relax.' When spin relaxes, the information encoded in it is lost. Therefore, we want the spin relaxation time to be as long as possible," said corresponding author Supriyo Bandyopadhyay, Ph.D., a professor in the Department of Electrical and Computer Engineering

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Researchers work toward enhancing the smallest electronic components

NanoTechWire  online


"In order to store and process information, the spin of an electron must be relatively robust. The most important property that determines the robustness of spin is the so-called 'spin relaxation time,' which is the time it takes for the spin to 'relax.' When spin relaxes, the information encoded in it is lost. Therefore, we want the spin relaxation time to be as long as possible," said corresponding author Supriyo Bandyopadhyay, Ph.D., a professor in the Department of Electrical and Computer Engineering at the VCU School of Engineering.

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Researchers spin out smaller electronics than ever before

Computer World  online


A research team of electrical and computer engineers in the U.S. is taking a new approach to electronics that harnesses the spin of an electron to store and process information. Dubbed 'spintronics', the new technology is expected to one day form a basis for the development of smaller, smarter, faster devices. Current day electronics are predominantly charge-based; that is, electrons are given more or less electric charge to denote the binary bits 0 and 1. Switching between the binary bits is accomplished by either injecting or removing charge from a device, which can, in more resource-intensive applications, require a lot of energy. "This [energy consumption] is a fundamental shortcoming of all charge based electronics," said lead researcher Supriyo Bandyopadhyay, a professor of Electrical and Computer Engineering at Virginia Commonwealth University.

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Researchers spin out smaller electronics than ever before

Computerworld  online


"The spin of an electron is like a tiny magnet with an associated direction of the magnetic moment, [which] can have only two stable directions: parallel to the external magnetic field or anti-parallel to the magnetic field," Bandyopadhyay explained.

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Spintronics Research May Lead to Faster Computers

CIO  online


"In order to store and process information, the spin of an electron must be relatively robust. The most important property that determines the robustness of spin is the so-called spin relaxation time, which is the time it takes for the spin to "relax." When spin relaxes, the information encoded in it is lost. Therefore, we want the spin relaxation time to be as long as possible," said corresponding author Supriyo Bandyopadhyay, PhD, a professor in the department of electrical and computer engineering at the VCU School of Engineering.

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Researchers study electron spin relaxation in organic nanostructures  online


Researchers have made an important advance in the emerging field of 'spintronics' that may one day usher in a new generation of smaller, smarter, faster computers, sensors and other devices, according to findings reported in today's issue of the journal Nature Nanotechnology. The research field of 'spintronics' is concerned with using the 'spin' of an electron for storing, processing and communicating information. The research team of electrical and computer engineers from the Virginia Commonwealth University’s School of Engineering and the University of Cincinnati examined the ‘spin’ of electrons in organic nanowires, which are ultra-small structures made from organic materials. These structures have a diameter of 50 nanometers. The spin of an electron is a property that makes the electron act like a tiny magnet. This property can be used to encode information in electronic circuits, computers, and virtually every other electronic gadget.

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Researchers improve quantum dot construction

EE Times  online


LINCOLN, Neb. — Fashioning themselves "latter-day Edisons," researchers at the University of Nebraska contend that their architecture for quantum-dot development is 500 percent better than its nearest competition. Quantum-dot devices, which use the quantum nature of electrons to switch between binary states, could be a solution to problems encountered by ever-shrinking conventional transistors. "We set a world record by demonstrating the largest nonlinear coefficient for a semiconductor quantum dot," said Supriyo Bandyopadhyay, the lead researcher. "Previous architectures have been highly praised for achieving a tiny percent increase, but we got a 500 percent increase with our design.

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Self-assembly route to quantum dots said to be simpler, cheaper than others

Laboratory Network  online


Quantum dots are nanoscale structures that have the potential for use as superdense computer data storage media, highly tunable lasers and nonlinear optical devices. But making them has always been difficult and expensive. At the University of Nebraska, Lincoln (UNL), however, researchers are working on a self-assembling dot production method they say is far simpler and potentially cheaper than standard methods. The conventional process for making quantum dot structures involves film growth (such as by atomic layer epitaxy or chemical vapor deposition), some type of lithographic patterning, and finally etching, such as by reactive ions. This is a complex series of steps. Now, UNL electrical engineering professor Supriyo Bandyopadhyay believes he's got a better way to make quantum dot structures.

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VCU honors six at faculty convocation

Virginia Commonwealth University  online


Bandyopadhyay, named Virginia’s Outstanding Scientist in 2016 by Gov. Terry McAuliffe, leads the Quantum Device Laboratory. His work centers on improving the speed and performance of electronic devices — and lowering their cost. The last piece is very important, Bandyopadhyay said. “An electronic gadget means absolutely nothing if it is affordable to only a tiny fraction of the world’s population,” he said. “What has motivated, informed and guided my research is to make things cheaper in a more efficient way so they become more accessible. Science is never for the 1 percent; it is always for the 100 percent.”

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Research Focus




Spintronics is the science and technology of storing, sensing, processing and communicating information with the quantum mechanical spin properties of electrons.

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Straintronics is the technology of rotating the magnetization direction of nanomagnets with electrically generated mechanical stress. It has applications in extremely energy-efficient Boolean and non-Boolean computing.

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Infrared photodetection



Infrared photodetectors have applications in night vision, collision avoidance systems, healthcare, mine detection, monitoring of global warming, forensics, etc. Room temperature detection of infrared light is enabled via quantum engineering in nanowires and by exploiting spin properties of electrons.

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Magneto-elastic non-volatile multiferroic logic and memory with ultralow energy dissipation



Room temperature nanowire IR, visible and UV photodetectors



Planar multiferroic/magnetostrictive nanostructures as memory elements, two-stage logic gates and four-state logic elements for information processing



Accessing of two-terminal electronic quantum dot comprising static memory



Electrochemical synthesis of quasi-periodic quantum dot and nanostructure arrays


Research Grants

Single nanowire spin valve based infrared photodetectors and equality bit comparators

National Science Foundation $ $375,000


Infrared light is not visible to the human eye. It is usually detected with semiconductor detectors which exhibit a change in their electrical resistance under infrared illumination. The relative change in resistance at room temperature is, however, quite small, which necessitates cooling the detector with liquid nitrogen. In this research, a novel detector will be demonstrated, which relies on light changing the detector's resistance by affecting the quantum mechanical spin properties of the electrons that carry current. With this principle of detection, it is possible to make the resistance change in the detector much larger at room temperature. Room temperature infrared detectors are used in night vision, forensic science, astronomy, missile defense, car-collision avoidance systems and monitoring of global warming, to name a few. Bit comparators are electronic devices that compare two digital (binary) bits of information and render a yes/no decision based on whether the two bits are the same or different. They are important ingredients of electronic circuits and are typically implemented with transistors which cannot remember the decision once the decision has been rendered. A comparator that exploits spin dependent properties and uses magnetic devices instead of transistors can remember the decision and also use less energy. The ability to remember makes it possible to build superior digital electronic circuits that are faster and more error-resilient. In this research, such a comparator will be demonstrated. This project will also integrate research with graduate and undergraduate education, K-12 outreach through the Dean's Early Research Initiative program, and minority enrichment through the Richmond Minorities in Engineering Partnership.

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NEB: Hybrid Spintronics and Straintronics: A New Technology for Ultra-Low Energy Computing and Signal Processing Beyond the Year 2020.

National Science Foundation $ 1,750,000


This project is awarded under the Nanoelectronics for 2020 and Beyond competition, with support by multiple Directorates and Divisions at the National Science Foundation as well as by the Nanoelectronics Research Initiative of the Semiconductor Research Corporation. The complementary metal oxide semiconductor field effect transistor, considered the workhorse of modern computing machinery, is inherently energy-inefficient because it is a charge-based digital switch. In contrast, a single-domain nanomagnet with uniaxial shape anisotropy, that encodes binary bits in its magnetization orientation, is much more energy-efficient because it is a spin-based switch in which the spins internally interact. Therefore, magnetic computing circuits hold a potential advantage over their electronic counterparts. That advantage however will be lost if the methodology used to switch the magnet becomes so energy-inefficient that it adds an exorbitant energy overhead. To this end, a hybrid spintronic/straintronic paradigm for switching magnets has been developed that reduces the energy dissipation by several orders of magnitude and heralds an ultra-energy-efficient magnetic computing and signal processing architecture. This project will: (1) develop all the modeling tools necessary to simulate these devices and their switching dynamics. They will incorporate the effects of device and circuit stochasticity and thermal fluctuations via appropriate models such as stochastic Landau-Lifshitz-Gilbert equations and/or Fokker-Planck equations; (2) demonstrate Bennett clocking and successful logic bit propagation in a digital gate array fabricated with nanolithography, where clocking is carried out with tiny voltages generating strain; (3) design energy-efficient neuromorphic architectures based on multi-state hybrid spintronic/straintronic synapses and neurons that can process analog signals; and (4) demonstrate image processing with straintronic/spintronic nodes communicating via spin waves to implement specific image morphing algorithms. These image processors will be extremely fast since they will rely on the physics of magnetic interactions between spin wave circuits and the collective activity of multiferroic magnetic cells to elicit the required functionality, without requiring any software or execution of instruction sets.

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Ultra-Low Power and Ultra-Sensitive Spintronic Nanowire Strain Sensor

National Science Foundation $ 330000


The research objective of this proposal is to investigate an ultra-low power, miniaturized, spintronic nanowire strain sensing device with an ultra-high sensitivity. This concept leverages two different physical phenomena: (i) stress induced magnetization rotation in nanoscale magnetostrictive materials; and (ii) change in the magneto-resistance of a "spin-valve" heterostructure nanowire consisting of magnetically-hard/spacer/magnetically-soft layers, which is induced by a rotation of the magnetization orientation of the soft layer. If successful, this could lead to a miniature strain sensor with an active area of 0.1mm x 0.1mm and with a sensitivity exceeding state-of-the-art, while consuming 2-3 orders of magnitude less power. Such a device could strongly impact several areas such as structural health monitoring, pressure, flow, acoustic and seismic sensing. This project will provide a strong multidisciplinary experience and mentorship for PhD students and will be leveraged to enhance innovative workshops on sensing and energy harvesting for high school students through the Math-Science Innovation Center. Under-represented K-12 students will be hosted for a month in summer under VCU's Richmond Area Program for Minorities in Engineering (RAPME) program and trained in nanofabrication under this project.

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A simulation hub for straintronics

Commonwealth Research Commercialization Fund $ 100,000


This grant is to establish a simulation hub for modeling magnetization dynamics of multiferroic nanomagnets under strain, with a view to applying them for ultra energy efficient computing.


EGRE 620: Electron Theory of Solids

Introduces graduate students to quantum theory of solids with emphasis on applications in solid state devices.

EGRE 621: Introduction to Spintronics

Introduces advanced graduate students to various facets of spintronics, spin physics, spin devices and elements of spin based quantum computing.

EGRE 610: Research Practices in Electrical and Computer Engineering

Introduces graduate students to grant writing, paper writing and perfects their skills in oral presentations.

Selected Articles

Dynamic Error in Strain-Induced Magnetization Reversal of Nanomagnets Due to Incoherent Switching and Formation of Metastable States: A Size-Dependent Study | IEEE Transactions on Electron Devices


Modulation of stress anisotropy of magnetostrictive nanomagnets with strain offers an extremely energy-efficient method of magnetization reversal. The reversal process, however, is often incoherent and hence, error-prone in the presence of thermal noise at room temperature. Occurrence of incoherent metastable states in the potential landscape of the nanomagnet can further exacerbate the error. Stochastic micromagnetic simulations at room temperature are used to understand and calculate energy dissipations and ...

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Super-giant magnetoresistance at room-temperature in copper nanowires due to magnetic field modulation of potential barrier heights at nanowire-contact interfaces | Nanotechnology


We have observed a super-giant (~ 10 000 000%) negative magnetoresistance at 39 mT field in Cu nanowires contacted with Au contact pads. In these nanowires, potential barriers form at the two Cu/Au interfaces because of Cu oxidation that results in an ultrathin copper oxide layer forming between Cu and Au. Current flows when electrons tunnel through, and/or thermionically emit over, these barriers. A magnetic field applied transverse to the direction of current flow along the wire deflects electrons toward one edge of the ...

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Experimental demonstration of acoustic wave induced magnetization switching of dipole coupled magnetostrictive nanomagnets for ultralow power computing | Applied Physics Letters


Dipole-coupled cobalt nanomagnet pairs of elliptical shape (with their major axes parallel) are delineated on 128° Y-cut lithium niobate. Each pair is initially magnetized along the major axis with a magnetic field forming the (↑↑) state. When an acoustic wave (AW) is launched in the substrate from interdigitated electrodes, the softer nanomagnet in the pair flips to produce the (↑↓) state since the AW modulates the stress anisotropy. This executes the logical NOT operation because the output bit encoded in the magnetization state of the softer nanomagnet becomes the logic complement of the input bit encoded in the magnetization of the harder one. The AW acts as a clock to trigger the NOT operation and the energy dissipated is a few tens of aJ. Such AW clocking can be utilized to flip nanomagnets in a chain sequentially to steer logic bits unidirectionally along a nanomagnetic logic wire with miniscule energy dissipation.

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Hybrid Spintronics/Straintronics: A Super Energy-Efficient Computing Paradigm Based on Interacting Multiferroic Nanomagnets | Spintronics in Nanoscale Devices


Computers—whether they are abacus, slide rules, hand-held calculators, laptops, desktops or supercomputers—have played an epochal role in human lives. Everything that we do today involves some calculation or data processing: the call we make in our cell phones involves information processing, the video game we play involves some form of calculation, and the TV animation we watch is based on processing voluminous amounts of data...

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Binary information propagation in circular magnetic nanodot arrays using strain induced magnetic anisotropy | Nanotechnology



Nanomagnetic logic has emerged as a potential replacement for traditional CMOS-based logic because of superior energy-efficiency. One implementation of nanomagnetic logic employs shape-anisotropic (eg elliptical) ferromagnets (with two stable magnetization orientations) as binary switches that rely on dipole-dipole interaction to communicate binary information. Normally, circular nanomagnets are incompatible with this approach since they lack distinct stable in-plane magnetization orientations to encode bits. However, circular ...

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Acoustic-Wave-Induced Magnetization Switching of Magnetostrictive Nanomagnets from Single-Domain to Nonvolatile Vortex States | Nano Letters


We report experimental manipulation of the magnetic states of elliptical cobalt magnetostrictive nanomagnets (with nominal dimensions of ∼340 nm × 270 nm × 12 nm) delineated on bulk 128° Y-cut lithium niobate with acoustic waves (AWs) launched from interdigitated electrodes. Isolated nanomagnets (no dipole interaction with any other nanomagnet) that are initially magnetized with a magnetic field to a single-domain state with the magnetization aligned along the major axis of the ellipse are driven into a vortex state by acoustic waves that modulate the stress anisotropy of these nanomagnets. The nanomagnets remain in the vortex state until they are reset by a strong magnetic field to the initial single-domain state, making the vortex state nonvolatile. This phenomenon is modeled and explained using a micromagnetic framework and could lead to the development of extremely energy efficient magnetization switching methodologies for low-power computing applications.

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Experimental Clocking of Nanomagnets with Strain for Ultralow Power Boolean Logic | Nano Letters


Nanomagnetic implementations of Boolean logic have attracted attention because of their nonvolatility and the potential for unprecedented overall energy-efficiency. Unfortunately, the large dissipative losses that occur when nanomagnets are switched with a magnetic field or spin-transfer-torque severely compromise the energy-efficiency. Recently, there have been experimental reports of utilizing the Spin Hall effect for switching magnets, and theoretical proposals for strain induced switching of single-domain magnetostrictive nanomagnets, that might reduce the dissipative losses significantly. Here, we experimentally demonstrate, for the first time that strain-induced switching of single-domain magnetostrictive nanomagnets of lateral dimensions ∼200 nm fabricated on a piezoelectric substrate can implement a nanomagnetic Boolean NOT gate and steer bit information unidirectionally in dipole-coupled nanomagnet chains. On the basis of the experimental results with bulk PMN–PT substrates, we estimate that the energy dissipation for logic operations in a reasonably scaled system using thin films will be a mere ∼1 aJ/bit.

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Giant voltage manipulation of MgO-based magnetic tunnel junctions via localized anisotropic strain: A potential pathway to ultra-energy-efficient memory technology | Applied Physics Letters


Voltage control of magnetization via strain in piezoelectric/magnetostrictive systems is a promising mechanism to implement energy-efficient straintronic memory devices. Here, we demonstrate giant voltage manipulation of MgO magnetic tunnel junctions (MTJ) on a Pb(Mg1/3Nb2/3)0.7Ti0.3O3 piezoelectric substrate with (001) orientation. It is found that the magnetic easy axis, switching field, and the tunnel magnetoresistance (TMR) of the MTJ can be efficiently controlled by strain from the underlying piezoelectric layer upon the application of a gate voltage. Repeatable voltage controlled MTJ toggling between high/low-resistance states is demonstrated. More importantly, instead of relying on the intrinsic anisotropy of the piezoelectric substrate to generate the required strain, we utilize anisotropic strain produced using a local gating scheme, which is scalable and amenable to practical memory applications. Additionally, the adoption of crystalline MgO-based MTJ on piezoelectric layer lends itself to high TMR in the strain-mediated MRAM devices.

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Strain effects on anisotropic magnetoresistance in a nanowire spin valve | Journal of Physics D: Applied Physics


The longitudinal magnetoresistance of a copper nanowire contacted by two cobalt contacts shows broad spin-valve peaks at room temperature. However, when the contacts are slightly heated, the peaks change into troughs which are signature of anisotropic magnetoresistance (AMR). Under heating, the differential thermal expansion of the contacts and the substrate generates a small strain in the cobalt contacts which enhances the AMR effect sufficiently to change the peak into a trough. This shows the extreme sensitivity of AMR to strain. The change in the AMR resistivity coefficient due to strain is estimated to be a few milli-ohm -m/microstrain.

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Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain | Nano Letters


A. K. Biswas, H. Ahmad, J. Atulasimha and S. Bandyopadhyay

Rotating the magnetization of a shape anisotropic magnetostrictive nanomagnet with voltage-generated stress/strain dissipates much less energy than most other magnetization rotation schemes, but its application to writing bits in nonvolatile magnetic memory has been hindered by the fundamental inability of stress/strain to rotate magnetization by full 180°. Normally, stress/strain can rotate the magnetization of a shape anisotropic elliptical nanomagnet by only up to 90°, resulting in incomplete magnetization reversal. Recently, we predicted that applying uniaxial stress sequentially along two different axes that are not collinear with the major or minor axis of the elliptical nanomagnet will rotate the magnetization by full 180°. Here, we demonstrate this complete 180° rotation in elliptical Co nanomagnets (fabricated on a piezoelectric substrate) at room temperature. The two stresses are generated by sequentially applying voltages to two pairs of shorted electrodes placed on the substrate such that the line joining the centers of the electrodes in one pair intersects the major axis of a nanomagnet at ∼ +30° and the line joining the centers of the electrodes in the other pair intersects at ∼ −30°. A finite element analysis has been performed to determine the stress distribution underneath the nanomagnets when one or both pairs of electrodes are activated, and this has been approximately incorporated into a micromagnetic simulation of magnetization dynamics to confirm that the generated stress can produce the observed magnetization rotations. This result portends an extremely energy-efficient nonvolatile “straintronic” memory technology predicated on writing bits in nanomagnets with electrically generated stress.

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Skewed Straintronic Magnetotunneling- Junction-Based Ternary Content- Addressable Memory—Part I | IEEE Transactions on Electron Devices


S. Dey Manasi. Md Mamun Al-Rashid, J. Atulasimha, S. Bandyopadhyay and A. R. Trivedi

This paper presents a ternary content-addressable memory (TCAM) cell based on a skewed straintronic magnetotunneling junction (MTJ) switch. A straintronic magnetotunneling junction (s-MTJ) is a three-terminal switch, where the resistance between twoof the terminals switches when a potential is applied to the third (gate) terminal that induces strain in the magnetostrictive free-layer. An s-MTJ is a highly energy-efficient switch that would dissipate only ∼aJ of energy during switching. This paper discusses a novel variant of s-MTJ, namely skewed s-MTJ (ss-MTJ), where the MTJ switching can be controlled by two gate terminals. The current through an ss-MTJ is minimum when the potentials at the first and second gate terminals (V2 and V3, respectively) obey the relation V3 = V2 + VF. Here, VF is a fixed voltage (“offset voltage”). Current in an ss-MTJ increases steeply when V2 and V3 deviate from the above “match” condition. This unconventional I–V characteristic of an ss-MTJ is exploited to design a non-Boolean TCAM cell based on just one transistor, one trench capacitor, and one ss-MTJ. We also discuss search and write operations in the ss-MTJ-TCAM cell, and show that the cell requires very small voltages to operate because of the unique I–V characteristics of the ss-MTJ.

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Skewed Straintronic Magnetotunneling-Junction-Based Ternary Content-Addressable Memory—Part II | IEEE Transactions on Electron Devices


S. Dey Manasi, Md Mamun Al-Rashid, J. Atulasimha, S. Bandyopadhyay and A. R. Trivedi

Part I of this paper discussed the design of a four-terminal skewed straintronic magnetotunneling junction (ss-MTJ) switch, and its adaptation to a non-Boolean “one transistor, one trench capacitor, and one ss-MTJ” ternary content-addressable memory (TCAM) cell. This part of the paper discusses a TCAM array based on ss-MTJ-TCAM cells and the associated peripherals for search operation. We show that non-Boolean associative processing of the ss-MTJ-TCAM cells enhances energy-efficiency and performance of an ss-MTJ-based TCAM array. The energy-delay-product (EDP) of ss-MTJ-based TCAM is compared against CMOS-based TCAM for a 144×256 array. The minimum EDP in ss-MTJ-based TCAM is ∼10.8× lower than the minimum EDP in CMOS-based TCAM. Additionally, the operational frequency at which the ss-MTJ-based design shows the minimum EDP is ∼9.4× higher than the respective frequency in the CMOS-based design. We also compare ss-MTJ-based TCAM against other state-of-the-art MTJ-based TCAMs. The comparison shows that the ss-MTJ-based TCAM also outperforms MTJ-based TCAMs in cell density, search delay, and search energy. Finally, we discuss implications of process variability in ss-MTJ to TCAM implementation and identify critical design parameters in ss-MTJ-based TCAM to enhance its robustness and area/ energy-efficiency.

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