Purdue's Self-assembled 'Nanorings' Could Boost Computer Memory...
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Purdue's Self-assembled 'Nanorings' Could Boost Computer Memory
WEST LAFAYETTE, Ind. - Recent nanotechnology research at Purdue University
could pave the way toward faster computer memories and higher density
magnetic data storage, all with an affordable price tag.
Just like the electronics industry, the data storage industry is on the move
toward nanoscale. By shrinking components to below 1/10,000th the width of a
human hair, manufacturers could make faster computer chips with more
firepower per square inch. However, the technology for making devices in
that size range is still being developed, and the smaller the components
get, the more expensive they are to produce.
Purdue chemist Alexander Wei may have come up with a surprisingly simple and
cheap solution to the shrinking data storage problem. Wei's research team
has found a way to create tiny magnetic rings from particles made of cobalt.
The rings are much less than 100 nanometers across - an important threshold
for the size-conscious computer industry - and can store magnetic
information at room temperature. Best of all, these "nanorings" form all on
their own, a process commonly known as self-assembly.
"The cobalt nanoparticles which form the rings are essentially tiny magnets
with a north and south pole, just like the magnets you played with as a
kid," said Wei, who is an associate professor of chemistry in Purdue's
School of Science. "The nanoparticles link up when they are brought close
together. Normally you might expect these to form chains, but under the
right conditions, the particles will assemble into rings instead."
The research appeared as a "Very Important Paper" in the November issue of
the chemistry journal Angewandte Chemie. Wei collaborated with lead author
Steven Tripp and Rafal Dunin-Borkowski, an electron microscopist at the
University of Cambridge.
The magnetic dipoles responsible for nanoring formation also produce a
collective magnetic state known as flux closure. There is strong magnetic
force, or flux, within the rings themselves, stemming from the magnetic
poles each particle possesses. But after the particles form rings, the net
magnetic effect is zero outside. Tripp developed conditions leading to the
self-assembly of the cobalt nanorings, then initiated a collaboration with
Dunin-Borkowski to study their magnetic properties. By using a technique
known as electron holography, the researchers were able to observe directly
the flux-closure states, which are stable at room temperature.
"Magnetic rings are currently being considered as memory elements in devices
for long-term data storage and magnetic random-access memory," Wei said.
"The rings contain a magnetic field, or flux, which can flow in one of two
directions, clockwise or counterclockwise. Magnetic rings can thus store
binary information, and unlike most magnets, the rings keep the flux to
themselves. This minimizes crosstalk and reduces error during data
When you turn on your computer, it loads its operating system and whatever
documents you are working on into its RAM, or random-access memory. RAM is
fast, enabling your computer to make quick changes to whatever is stored
there, but its chief drawback is its volatility - it cannot perform without
a continuous supply of electricity. Many people have experienced the
frustration of losing an unsaved document when their computer suddenly
crashes or loses power, causing all the data stored in RAM to vanish.
"Nonvolatile memory based on nanorings could in theory be developed," Wei
said. " For the moment, the nanorings are simply a promising development."
Preliminary studies have shown that the nanorings' magnetic states can be
switched by applying a magnetic field, which could be used to switch a
nanoring "bit" back and forth between 1 and 0. But according to Wei, perhaps
the greatest potential for his group's findings lay in the possibility of
combining nanorings with other nanoscale structures.
"Integrating the cobalt nanorings with electrically conductive nanowires,
which can produce highly localized magnetic fields for switching flux
closure states, is highly appealing." he said. "Such integration may be
possible by virtue of self-assembly."
Several research groups have created magnetic rings before but have relied
on a "top-down" manufacturing approach, which imposes serious limitations on
"The fact that cobalt nanoparticles can spontaneously assemble into rings
with stable magnetic properties at room temperature is really remarkable,"
Wei said. "While this discovery will not make nonvolatile computer memory
available tomorrow, it could be an important step towards its eventual
development. Systems like this could be what the data storage industry is
Wei's group is associated with the Birck Nanotechnology Center, which will
be one of the largest university facilities in the nation dedicated to
nanotechnology research when construction is completed in 2005. Nearly 100
groups associated with the center are pursuing research topics such as
nanometer-sized machines, advanced materials for nanoelectronics and
Funding for Wei's research was provided in part by the National Science
Foundation and the Department of Defense.
Editor's Note: The original news release can be found here.
Do Wah Ditty
"Our country puts $1 billion a year up to help feed the hungry. And we're by
far the most generous nation in the world when it comes to that, and I'm
proud to report that. This isn't a contest of who's the most generous. I'm
just telling you as an aside. We're generous. We shouldn't be bragging about
it. But we are. We're very generous."
- Washinton D.C., July 16, 2003