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February 01, 2002 --
Low-cost flexible electronics and better computer data storage might
result from the world's first light-tunable plastic magnet, just
developed at Ohio State University and the University of Utah.
The researchers 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.
"This opens opportunities for light-controlled magnetic materials,
which could lead to new electronic-storage and computer-storage
devices in the future," said Joel S. Miller, a professor of
chemistry at the University of Utah.
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 Center for Materials Research.
The magnet functions up to a temperature of 75 degrees Kelvin (about
minus 200 degrees Celsius or minus 325 degrees Fahrenheit). 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 Miller. They describe the magnet in the current issue of the
journal Physical Review Letters, in a paper coauthored with Dusan
Pejakovic, a doctoral student in physics at Ohio State, and Miller's
former graduate student Chitoshi Kitamura, now at the Himeji Institute
of Technology in Japan.
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-tunable
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.
The researchers 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 percent 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 neighbor molecules
to change shape, too," Epstein explained.
Worldwide, scientists and engineers are working to develop computer
data storage based on light and magnetism. Such magneto-optical
systems theoretically would work faster and much more efficiently
than traditional electronics. A light-tunable 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. Today, liquid nitrogen costs less per gallon
than milk - roughly $2. Manufacturers that bought it in bulk would
pay even less.
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.
He and his colleagues are now trying to improve the magnet by exploring
different chemical compositions.
The Air Force Office of Scientific Research and the United States
Department of Energy funded this work.
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| Media Contacts: |
| Joel Miller, professor of chemistry, University
of Utah |
office (801) 585-5455, home (801) 273-9647,
jsmiller@chemistry.utah.edu |
Arthur J. Epstein, professor of physics and chemistry,
Ohio State University
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(614) 292-1133; Epstein.2@osu.edu |
| Pam Frost Gorder, university relations, Ohio State
University |
(614) 292-9475; Gorder.1@osu.edu |
| Lee Siegel, science news specialist, University
of Utah Public Relations |
office (801) 581-8993,
cell (801) 244-5399, leesiegel@ucomm.utah.edu |
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