Plastic shows promise for spintronics, magnetic computer memory

Researchers at Ohio State University and their colleagues have expanded the possibilities for a new kind of electronics, known as spintronics.

Though spintronics technology has yet to be fully developed, it could result in computers that store more data in less space, process data faster, and consume less power. It could even lead to computers that “boot up” instantly, said Arthur J. Epstein, professor of physics and chemistry and director of Ohio State’s Center for Materials Research.

Spintronics uses magnetic fields to control the spin of electrons. In the current issue of the journal Advanced Materials, Epstein and his coauthors report using a magnetic field to make nearly all the moving electrons inside a sample of plastic spin in the same direction, an effect called spin polarization. Achieving spin polarization is the first step in converting the plastic into a device that could read and write spintronic data inside a working computer.

What’s unique about this work is that the researchers achieved spin polarization in a polymer, which offers several advantages over silicon and gallium arsenide — the traditional materials for electronics.

Epstein and long-time collaborator Joel S. Miller, professor of chemistry at the University of Utah, co-authored the paper with Vladimir N. Prigodin, a research specialist; Nandyala P. Raju, a research associate; and Konstantin I. Pokhodynya, a visiting researcher, all of Ohio State.

Since the mid 1980s, Epstein and Miller have been developing plastic electronics, most recently a plastic magnet that conducts electricity. Epstein characterized this latest project as part of a natural progression of their work toward spintronics.

“Electronics and magnetism have transformed modern society,” said Epstein. “The advent of plastic electronics opens up many opportunities for new technologies such as flexible displays and inexpensive solar cells.”

“With this latest study, we’ve now shown that we can make all of the components that go into spintronics from plastics,” Epstein continued. “So it is timely to bring all these components together to make plastic spintronics.”

Current efforts to develop spintronics with traditional inorganic semiconductors have been stymied by the fact that most such materials aren’t magnetic, except at very low temperatures. Creating a cryogenically cold environment inside a hot computer interior — where temperatures reach up to 120 F (50 C) — would be expensive. Plus, any cooling equipment would take up precious real estate inside a small device.

That’s why the Ohio State and Utah researchers chose a plastic called vanadium tetracyanoethanide. The material exhibits magnetic qualities at high temperatures, even above the boiling point of water (212 F, 100 C), so it could possibly function inside a computer without special cooling equipment.

Why are researchers so interested in spintronics? Normal electronics encode computer data based on a binary code of ones and zeros, depending on whether an electron is present in a void within the material. But in principle, the direction of a spinning electron — either “spin up” or “spin down” — can be used as data, too. So spintronics would effectively let computers store and transfer twice as much data per electron.

Another bonus: once a magnetic field pushes an electron into a direction of spin, it will keep spinning the same way until another magnetic field causes the spin to change. This effect can be used to very quickly access magnetically stored information during computer operation — even if the electrical power to a computer is switched off between uses. Data can be stored permanently, and is nearly instantly available anytime, no lengthy “boot up” needed.

Plastic spintronics would weigh less than traditional electronics and cost less to manufacture, Epstein said. Today’s inorganic semiconductors are created through multiple steps of vacuum deposition and etching. Theoretically, inexpensive ink-jet technology could one day be used to quickly print entire sheets of plastic semiconductors for spintronics.

Using plastic may solve another problem currently faced by developers: spinning electrons must be able to move smoothly between different components. But traveling from one material to another can sometimes knock an electron off-kilter. Data encoded in that electron’s spin would be lost.

For this reason, Epstein, Miller, and their colleagues are working on transferring spinning electrons through a layered stack of different magnetic and non-magnetic polymers.

The U.S. Department of Energy and the Army Research Office supported this work.

Contact: Arthur J. Epstein, (614) 292-1133; Epstein.2@osu.edu
Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu