Supriyo Bandyopadhyay, Ph.D.

Gov. Northam recognizes Outstanding Faculty Award recipients

Augusta Free Press  print

2018-03-02

Supriyo Bandyopadhyay is commonwealth professor of electrical and computer engineering at Virginia Commonwealth University where he has worked for 17 years as director of the Quantum Device Laboratory. Bandyopadhyay was named Virginia’s Outstanding Scientist by Governor Terry McAuliffe in 2016.

Governor Northam recognizes outstanding faculty awards recipients

Virginia Secretary of Education  online

2018-03-01

RICHMOND - Governor Ralph Northam today recognized 12 Virginia educators as recipients of the 32nd annual Outstanding Faculty Award for excellence in teaching, research, and public service. The annual Outstanding Faculty Award program is administered by the State Council of Higher Education for Virginia (SCHEV) and sponsored by Dominion Energy. “These outstanding educators have devoted their lives to research and teaching.” said Governor Northam. “Each has a proven track record of academic excellence and giving back to their communities. I am pleased to support these wonderful Virginia teachers and it is my privilege to recognize each of them with the Outstanding Faculty Award.” The recipients, all faculty members from colleges and universities across the Commonwealth, were honored today during an awards ceremony at the Jefferson Hotel in Richmond. “The 12 educators that we are recognizing play a pivotal role in the lives and successes of the people they teach and inspire,” said Secretary of Education Atif Qarni. “With this award we thank them for their service to students, to their institutions, and to the Commonwealth.” “We are fortunate that Virginia is home to one of the world’s great systems of higher education,” said Peter Blake, director of SCHEV. “The Outstanding Faculty Awards recognize faculty members who have dedicated their lives to research, teaching, and mentorship. Their work improves the lives of everyone in the Commonwealth.” The awards are being made through a $75,000 grant from the Dominion Energy Charitable Foundation, the philanthropic arm of Dominion Energy and the sponsor of the Outstanding Faculty Awards for the 14th year. “Dominion Energy is pleased to partner with SCHEV once again to honor Virginia’s outstanding educators,” said Hunter A. Applewhite, president of the Dominion Energy Charitable Foundation. “Every year, I am impressed and humbled by the dedication shown by these teachers and researchers to guide and inspire our young people to excel in the classroom and in life.”

VCU Engineering Professor receives Governor's highest award for Teaching

Virginia Commonwealth University  online

2018-02-07

Supriyo Bandyopadhyay, Ph.D., Commonwealth Professor in the Virginia Commonwealth University School of Engineering, has been named a recipient of the 2018 State Council of Higher Education for Virginia (SCHEV) Outstanding Faculty Award

VCU honors six at faculty convocation

Virginia Commonwealth University  online

2017-08-25

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.”

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

Times of India  online

2016-07-12

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.

Putting a New Spin on Electronics

Community Idea Stations  

2016-05-04

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...

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

The Virginia Pilot  

2016-02-05

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...

Single-electron devices come together

NanoTechWeb  

2015-09-23

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...

Straintronic spin neuron may greatly improve neural computing

ECN Magazine  online

2015-07-09

"Most computers are digital in nature and process information using Boolean logic," Bandyopadhyay told Phys.org. "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."

'Straintronic spin neuron' may greatly improve neural computing

Phys.org  online

2015-07-08

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.

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

Phys.org  online

2014-09-03

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.

Researchers aim for energy-harvesting CPUs

EE Times  online

2011-09-01

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.

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

Kurzweil  online

2011-08-17

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]

Strain and spin could drive ultralow energy computers

Institute of Physics: PhysicsWorld  online

2011-01-27

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.

Dr. Supriyo Bandyopadhyay: Spintronics Drives Next-Gen Computing

NanoScienceWorks  online

2008-01-17

“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 NanoScineceWorks.org. Dr. Bandyopadhyay also serves as Professor of Electrical Engineering and Professor of Physics at VCU.

Spintronics: Making Computers Smaller and Faster

Science Daily  online

2007-03-27

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.

Spintronics, the Way to Faster and Smaller Computers

Softpedia News  online

2007-03-27

"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

Researchers spin out smaller electronics than ever before

Computer World  online

2007-03-23

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.

Spintronics Research May Lead to Faster Computers

CIO  online

2007-03-20

"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.

Researchers study electron spin relaxation in organic nanostructures

Phys.org  online

2007-03-19

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.

Researchers improve quantum dot construction

EE Times  online

2000-11-28

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.

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

Laboratory Network  online

2000-11-16

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.

Quantum Mechanics May Contribute to Military Surveillance

The Daily Nebraskan  online

2000-11-21

Quantum dots promise to pave the way for a new world in technology.As minuscule entities that are 10,000 times smaller than the width of a human hair, quantum dots have properties which make them the ideal building blocks for a new quantum computing system.Unlike traditional computers that rely on classical physics, the new generation of computers would operate under the strange and fascinating laws of quantum mechanics."With quantum mechanics it is possible for an entity to coexist in two different states at the same time," said electrical engineering professor Supriyo Bandyopadhyay.The ability to be in two different places simultaneously is known as quantum parallelism."The concept of a parallel existence is difficult to explain," Bandyopadhyay. "It appears very strange and mystical."

Spintronics

Nanostructures

2017-01-03

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

Straintronics

Nanomagnets

2017-01-03

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.

Infrared photodetection

Nanowires

2017-01-03

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.

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

9379162

2016-06-28

Room temperature nanowire IR, visible and UV photodetectors

8946678

2015-02-03

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

8921962

2014-12-30

Accessing of two-terminal electronic quantum dot comprising static memory

6501676

2002-12-31

Electrochemical synthesis of quasi-periodic quantum dot and nanostructure arrays

5747180

Single nanowire spin valve based infrared photodetectors and equality bit comparators

National Science Foundation $ 425,000

2017-01-04

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.

Energy-efficient strain assisted spin transfer torque memory

National Science Foundation $ 402392

2018-05-21

Non-volatile random access memory (NV-RAM) is often built with a device called spin transfer torque random access memory (STT-RAM), the main constituent of which is a circular nano-magnet. A bit is "written" into the nano-magnet by passing a spin-polarized current whose polarity determines whether bit "1" or bit "0" is written. The energy barrier between these states prevents the magnetization from switching spontaneously due to thermal noise, making the device non-volatile. Unfortunately, the energy dissipated in the writing current is 100-1000 times more than the energy dissipated in today's CMOS devices, which is a large cost to pay for non-volatility. This project seeks to demonstrate that temporarily reducing the energy barrier between the "up" and "down" magnetization states with surface acoustic waves (SAW) can significantly lower the current needed to write a bit and reduce the energy dissipation by orders of magnitude. This would make the SAW-assisted STT-RAM ideal for embedded processors, internet of things, large data centers and cyber-physical systems requiring low energy memory. At least 3 PhD students would be trained on the techniques of complementary nano-fabrication, nano-characterization and computer modeling. The investigators will hold a nano-magnetism workshop for high school students and will host under-represented K-12 students in their labs for a summer month, as well as leverage the "Nano-Days" program to reach out to high school students.

A simulation hub for straintronics

Commonwealth Research Commercialization Fund $ 100,000

2017-01-03

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.

Acquisition of a Physical Properties Measurement System

National Science Foundation $ 281610

2017-08-21

This Major Research Instrumentation award will help acquire a Physical Properties Measurement System (PPMS) with autorotation, supplementary electrical measurements and low and high temperature capabilities coupled with a Vibrating Sample Magnetometer (VSM) at Virginia Commonwealth University (VCU). Additionally, the cryogen-free PPMS/VSM would enable making robust low temperature measurements without requiring liquid helium to extremely sensitive magnetic measurements. The equipment will help enhance research and teaching efforts at VCU and nearby universities including those related to Smart Materials, Electron Theory of Solids, Solid State Physics and Experimental techniques and Foundations of Nanoscience. Improved facilities at VCU will impact high tech skills imparted to both regular and part time students which eventually will help industries located in northeast USA.

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.

EGRE 303: Solid State Devices

Introduces undergraduates to the physics and operating principles of electronic and optical devices.

2017-05-26

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.

2017-07-01

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.

2017-07-01

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.

2017-11-01

D. B. Gopman, V. Sampath, H. Ahmad, S. Bandyopadhyay and J. Atulasimha

We present the measurements of the static and dynamic properties of polycrystalline iron–gallium films, ranging from 20 to 80 nm and sputtered from an Fe0.8Ga0.2 target. Using a broadband ferromagnetic resonance setup in a wide frequency range, perpendicular
standing spin-wave resonances were observed with the external static magnetic field applied in-plane. The field corresponding to the strongest resonance peak at each frequency is used to determine the effective magnetization, the g-factor, and the Gilbert damping.
Furthermore, the dependence of spin-wave mode on field-position is observed for several frequencies. The analysis of broadband dynamic properties allows determination of the exchange stiffness A = (18±4) pJ/m and Gilbert damping α = 0.042±0.005 for 40 and 80 nm thick films. These values are approximately consistent with values seen in epitaxially grown films, indicating the potential for the industrial fabrication of magnetostrictive FeGa films for microwave applications.

2017-09-20

J. L. Drobitch, Md. A. Abeed and S. Bandyopadhyay

We describe an approach to implement precessional switching of a perpendicular-magnetic-anisotropy magneto-tunneling-junction (p-MTJ), without using any magnetic field. The switching is accomplished with voltage-controlled-magnetic-anisotropy (VCMA), spin transfer torque (STT) and mechanical strain. The soft layer of the p-MTJ is magnetostrictive and the strain acts as an effective in-plane magnetic field around which the magnetization of the soft layer precesses to complete a flip. A two-terminal energy-efficient p-MTJ based memory cell, that is compatible with crossbar architecture and high cell density, is designed.

2018-09-05

M. A. Abeed, J. Atulasimha and S. Bandyopadhyay

We theoretically study the effect of a material defect (material void) on switching errors associated with magneto-elastic switching of magnetization in elliptical magnetostrictive nanomagnets having in-plane magnetic anisotropy. We find that the error probability increases significantly in the presence of the defect, indicating that magneto-elastic switching is particularly vulnerable to material imperfections. Curiously, there is a critical stress value that gives the lowest error probability in both defect-free and defective nanomagnets. The critical stress is much higher in defective nanomagnets than in defect-free ones. Since it is more difficult to generate the critical stress in small nanomagnets than in large nanomagnets (having the same energy barrier for thermal stability), it would be a challenge to downscale magneto-elastically switched nanomagnets in memory and other applications where reliable switching is required. This is likely to be further exacerbated by the presence of defects

2018-08-29

Noel D'Souza, Ayan Biswas, Hasnain Ahmad, Mohammad Salehi Fashami, Md Mamun Al-Rashid, Vimal Sampath, Dhritiman Bhattacharya, Md Ahsanul Abeed, Jayasimha Atulasimha and Supriyo Bandyopadhyay

The need for increasingly powerful computing hardware has spawned many ideas stipulating, primarily, the replacement of traditional transistors with alternate 'switches' that dissipate miniscule amounts of energy when they switch and provide additional functionality that are beneficial for information processing. An interesting idea that has emerged recently is the notion of using two-phase (piezoelectric/magnetostrictive) multiferroic nanomagnets with bistable (or multi-stable) magnetization states to encode digital information (bits), and switching the magnetization between these states with small voltages (that strain the nanomagnets) to carry out digital information processing. The switching delay is ~1 ns and the energy dissipated in the switching operation can be few to tens of aJ, which is comparable to, or smaller than, the energy dissipated in switching a modern-day transistor. Unlike a transistor, a nanomagnet is 'non-volatile', so a nanomagnetic processing unit can store the result of a computation locally without refresh cycles, thereby allowing it to double as both logic and memory. These dual-role elements promise new, robust, energy-efficient, high-speed computing and signal processing architectures (usually non-Boolean and often non-von-Neumann) that can be more powerful, architecturally superior (fewer circuit elements needed to implement a given function) and sometimes faster than their traditional transistor-based counterparts. This topical review covers the important advances in computing and information processing with nanomagnets, with emphasis on strain-switched multiferroic nanomagnets acting as non-volatile and energy-efficient switches—a field known as 'straintronics'. It also outlines key challenges in straintronics.

2018-11-23

Sucheta Mondal, Md Ahsanul Abeed, Koustuv Dutta, Anulekha De, Sourav Sahoo, Anjan Barman, and Supriyo Bandyopadhyay

Magnetoelastic (or “straintronic”) switching has emerged as an extremely energy-efficient mechanism for switching the magnetization of magnetostrictive nanomagnets in magnetic memory and logic, and non-Boolean circuits. Here, we investigate the ultrafast magnetodynamics associated with straintronic switching in a single quasielliptical magnetostrictive Co nanomagnet deposited on a piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 substrate using time-resolved magneto-optical Kerr effect (TR-MOKE) measurements. The pulsed laser pump beam in the TR-MOKE plays a dual role: it causes precession of the nanomagnet’s magnetization about an applied bias magnetic field and it also generates surface acoustic waves in the piezoelectric substrate that produce periodic strains in the magnetostrictive nanomagnet and modulate the precessional dynamics. This modulation gives rise to intriguing hybrid magnetodynamical modes in the nanomagnet, with a rich spin-wave texture. The characteristic frequencies of these modes are 5–15 GHz, indicating that strain can affect magnetization in a magnetostrictive nanomagnet in time scales much smaller than 1 ns (∼100 ps). This can enable ∼10 GHz range magnetoelastic nano-oscillators that are actuated by strain instead of a spin-polarized current, as well as ultrafast magnetoelectric generation of spin waves for magnonic logic circuits, holograms, etc.