Multidisciplinary Team Embraces New Paradigm for Magnetic Storage

In 1956, IBM shipped the first hard drive for the first commercial computer, and it used a moving-head hard disk drive for memory storage. The drive held only five megabytes of data, and the system was the size of two refrigerators. In 1980, commercially available hard drives could hold one gigabyte, but were still the size of a refrigerator. In the 1990s, with the advent of portable computers, a hard drive holding a terabyte of data had shrunk to an inch. This revolution was made possible by advances in magnetic storage.

High density magnetic storage, however, is nearing its superparamagnetic limit, the maximum number of bits per square inch that is commercially feasible on a magnetic storage device. A multi-disciplinary, multi-university team of physicists, electrical engineers and materials scientists are making discoveries in nanomagnetism that target this barrier. The Virginia Nano-Computing Group leads the nanomagnetism research thrust, under the direction of Avik Ghosh, professor of electrical and computer engineering and physics at the University of Virginia. A $3.5 million grant awarded in 2018 from the Defense Advanced Research Projects Agency’s Topological Excitations in Electronics Program supports their work.

The nanomagnetism research team has embraced a new paradigm to engineer tiny information-carrying bits, called skyrmions. The skyrmion has a tiny vortex pattern whose inertia fights against thermal fluctuations. This unique configuration gives the skyrmion an advantage in the quest to simultaneously increase memory, processing speed and power economy for conventional memory and unconventional computing.

Team members aim to create skyrmions smaller than 10 nanometers that remain stable at room temperatures. The process is similar to writing a figure on a piece of paper. In place of ink, the team uses electric current; in place of the paper, the team uses a ferromagnetic material deposited on a heavy metal surface.

Prasanna Balachandran, assistant professor in materials science and engineering and mechanical and aerospace engineering at UVA, uses machine learning and computational materials science to predict new materials with favorable phase transition temperatures and other physical properties needed to support ultra-small skyrmions at room-temperature.

A research group led by Joseph Poon, UVA William Barton Rogers Professor of Physics, grows thin films of magnetic materials that are predicted to have small skyrmions. Ghosh’s group simulates skyrmions’ dynamics in thin films to learn how to drive them and how they consume and expend energy as they go.

Mircea Stan, Virginia Microelectronics Consortium Professor at UVA, translates these dynamics into device and circuit applications. Andrew Kent, professor of physics at New York University, leads an allied effort to experimentally measure skyrmions’ transport properties in a device configuration. Geoffrey S.D. Beach, professor of materials science and engineering at the Massachusetts Institute of Technology, uses state-of-the-art modeling and measuring techniques to image these skyrmions and experimentally understand their size and dynamics.

This overall theory-driven experimental approach distinguishes the nanomagnetism research team’s expertise. “We have modeling at multiple levels, from materials to transport all the way to circuits, as well as an entire suite of experimental characterization,” Ghosh said. This collaboration enables systemic experimentation to better understand the physics involved, and to test and refine their predictions. Ultimately, the collaboration will enable the team to create ideal materials for ultra-small, ultra-fast and stable skyrmions with which to engineer high density, ultrafast, all electronic solid-state memory devices.