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Sci Tech
Tuning plastic magnets with light
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Plastic magnets and light-responsive magnets have been developed earlier. But this is the first time both the technologies have been married into one. This technology could one day lead to a magneto-optical system for writing and erasing data from computer hard drives.
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LOW-COST, flexible electronics and better computer data storage might result from the world's first light-tuneable plastic magnet, just developed at Ohio State University. With colleagues at the University of Utah, researchers here developed a plastic material that becomes 1.5 times more magnetic when blue light shines on it. Green light partially reverses that effect.
Although possible applications are years away, this technology could one day lead to a magneto-optical system for writing and erasing data from computer hard drives.
While other scientists have developed plastic magnets, and yet others have developed light-responsive magnets, this is the first material to marry both technologies into one -- and at record-high temperatures, explained Arthur J. Epstein, professor of physics and chemistry and director of Ohio State's Centre for Materials Research.
The magnet functions up to a temperature of 75 Kelvin (about minus -200ºC, or minus 325ºF). This temperature, which approaches that of today's "high-temperature" superconductors, is a key factor for enabling commercial applications for the technology.
The magnet resulted from a 25-year collaboration between Epstein and Joel S. Miller, professor of chemistry at University of Utah. The magnet has been described in the journal Physical Review Letters.
Though the working temperature of the magnet is very cold, it represents an important first step toward future light-based forms of electronics, Epstein said.
"Now that we've proven it's possible to make a light-tuneable magnet out of an organic, or `plastic,' material, we can use what we know about organic chemistry to further improve its properties," Epstein said. "We may someday even be able to improve it to the point that it works at room temperature."
The plastic magnet is made from a polymer comprised of tetracyanoethylene (TCNE) combined with manganese (Mn) ions -- atoms of the metal manganese with electrons removed.
Epstein and his colleagues deposited the Mn-TCNE powder into a thin film. After they `charged' the material with an initial six-hour dose of blue laser light, the magnet maintained a higher degree of magnetism -- 150 per cent of its normal level -- even in the dark.
Green laser light reversed the effect somewhat, by decreasing the material's magnetism to 60 percent of its normal level.
Why would light have this effect? The researchers think the different wavelengths of blue and green light cause the TCNE molecules to change shape in different ways.
"Once one molecule in the magnet locks into a different shape, its magnetism changes, and it encourages its neighbour molecules to change shape, too," Epstein explained.
Worldwide, scientists and engineers are working to develop computer data storage based on light and magnetism.
Theoretically, such magneto-optical systems would work faster and much more efficiently than traditional electronics. A light-tuneable magnet would be a critical component, because it would allow computers to write and erase data magnetically.
Because the new magnet works at temperatures up to 75 Kelvin, it could one day be employed in a device that was cooled by a refrigerator or by liquid nitrogen. .
But such applications are years away, said Epstein. "We'd like to see the magnet work at higher temperatures before we talk about commercial development," he said.
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