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Nanomagnetic Devices Present an Attractive Solution

AUTHOR: ND Staff

PUBLISHED: June 18, 2014

For the last 40 years conventional electronic technology (CMOS) has relied on shrinking transistors to produce smaller, faster, and cheaper devices (cell phones, laptop computers, iPods, and more). The laws of physics prevent these devices from working below a certain size. Because of this, researchers across the country have been searching for a new logic device to either replace or augment CMOS technology. University of Notre Dame researchers have achieved a series of firsts, including their most recent accomplishment, that may well prove to be a giant leap toward achieving a new type of processing system, one driven by nanomagnets and their interactions rather than electric current flow.

In 1997, Notre Dame researchers were the first to physically demonstrate Quantum-dot Cellular Automata (QCA), a transistorless approach to computing that moves and processes information via nearest-neighbor interactions rather than electric current. Less than ten years later, researchers at Notre Dame were the first to demonstrate logic gates with a magnetic implementation of this device architecture. This was an important first step toward showing that nanoscale magnets could ultimately perform more complex computations, computations that would require much less energy than equivalent CMOS circuits.

Michael Niemier
Michael Niemier, Assistant Professor, Computer Science and Engineering

Assistant Professor Michael Niemier and a team from the departments of computer science and engineering and electrical engineering have been pursuing the design of circuit elements constructed with nanoscale magnets and using the QCA device architecture. In magnetic QCA (MQCA), logical operations and data flow are accomplished by manipulating the polarizations of nanoscale magnets. Niemier and his team are moving toward another “first”; they have designed MQCA structures that should facilitate more complex, circuit-level tasks. They have also demonstrated how these structures interact with the on-chip drive circuitry currently envisioned for MQCA-based systems through simulations and are proceeding to prototype testing.

Previous efforts of this nature had suggested the components required for a functionally complete logic set, but there was still a large gap between basic MQCA devices and computationally interesting MQCA systems. The Notre Dame team narrowed this gap by designing unique circuit structures essential for building MQCA systems. They used physical level simulation to demonstrate how external stimuli affect the logic state of individual magnets of various sizes and shapes. Within this study, they (a) ensured that all of the structures required to build a circuit could be controlled with implementable, on-chip drive circuitry, (b) designed structures that allowed data to flow orthogonally in the direction of the external stimuli, and (c) have proposed designs for crossing two logical signals with nanomagnets.

These studies revealed a number of physical and external design parameters, such as nanomagnetic shapes and sizes and clocking field (the external stimuli) strengths and shapes, which are key to circuit-level behavior. Careful selection of these parameters helps not only to facilitate computationally interesting circuits but can also improve circuit performance.

According to Niemier, the next step is fabricating MQCA-based systems, which should be fairly straightforward. “Nanomagnets can be made using conventional lithography or by leveraging electron beam lithography and liftoff to form specific patterns of magnetic material.” Researchers could also employ imprint lithography where the imprint is used to make molds, and then the molds can be used to make the nanomagnet shapes. Niemier and his team believe that these methods should be compatible with, and can take advantage of, advances in current CMOS fabrication techniques.

Another advantage to nanomagnetic technology is that the magnets are inherently resistant to radiation. Thus, any type of MQCA system placed in space would be immune to the effects of radiation, which eventually destroy traditional CMOS chips.

Still in the fundamental stages of research, Notre Dame is on the road to another first: developing an all-magnetic system that offers more complex computations and uses less energy.

SUGGESTED READING

Niemier, M., Dingler, A., Hu, X. Sharon, Alam, M. Tanvir, Bernstein, G.H., and Porod, W., “Bridging the Gap between Nanomagnetic Devices and Circuits,” in the 26th IEEE International Conference on Computer Design, Lake Tahoe, CA, Oct. 12-15, 2008, 506-513.

Niemier, M., Crocker, M., and Hu, X. Sharon, “Fabrication Variations and Defect Tolerance for Nanomagnet-based QCA,” in the 23rd IEEE International Symposium on Defect and Fault Tolerance in VLSI Systems, Cambridge, MA, Oct. 1-3, 2008, 534-542.

Orlov, A., Imre, A., Csaba, G., Ji, L., Porod, W., and Bernstein, G.H., “Magnetic Quantum-dot Cellular Automata: Recent Developments and Prospects,” Journal of Nanoelectronics and Optoelectronics, 2008, 3, 1-14.

Imre, A., Csaba, G., Ji, L., Orlov, A., Bernstein, G.H., and Porod, W., “Majority Logic Gate for Magnetic Quantum-dot Cellular Automata,” Science, 2006, 311, 5758, 205-208.

Categories:  Energy Research

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