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Brown University Magnet Provides Promise for
Electronics Advances
Tuscaloosa, AL,
Feb 15: Shiny, black magnetic films, about the size of a penny and made
by University of Alabama researchers, are central to a discovery of how to
conduct resistance-free electricity in a manner previously thought impossible.
The research, conducted by scientists at Brown University, the Delft University
of Technology in the Netherlands and UA, provides promising new leads for future
electronics development and will publish in the Feb.16 issue of Nature.
Scientists have demonstrated the ability to sandwich the magnetic material,
chromium dioxide, between two superconductors in a way that allows an electrical
current to pass through the magnetic material, while retaining the
resistance-free benefits of the superconductors.
“Our role has primarily been in making these unique, high-quality magnetic
materials,” said Dr. Arunava Gupta, a researcher in UA’s Center for Materials
for Information Technology, known as MINT, and a co-author of the paper to
publish in Nature. While the samples’ surface area is about the same as a
penny’s, the samples are considerably thinner, measuring only 1,000 atoms.
Previously, scientists had only been able to pass a current between two
superconductors that were sandwiching magnetic materials, while the
superconductors were only three to four atoms apart. In the latest discovery,
the current traveled through the “sandwich” with the superconductors 300 times
farther apart.
The discovery shows that some related long-held physics theories are incomplete,
and it could also later positively impact a new field of electronics called
“spintronics,” the researchers say. In spin-based electronics, or spintronics,
the spin of electrons, as well as their charge, is captured and used in
producing such things as improved circuits and computer chips.
The discovery indicates the presence of a rare type of “spin triplet” conversion
of the superconducting current in the magnetic layer, the researchers say.
The benefit of superconductors, central in advances such as magnetic resonance
imaging machines and passenger trains that travel at high speeds while
levitating above their tracks, lies in these materials’ ability to conduct
electricity without resistance. Resistance results in energy loss and is thereby
undesired.
One of Gupta’s former UA graduate students, Dr. Guoxing Miao, now a
post-doctoral researcher at MIT, is another of the paper’s co-authors.
Gupta, who is also a professor of chemistry and chemical engineering at UA, says
potential applications of the discovery are difficult to predict, but he said it
has the potential to lead to electronic devices with significantly lower energy
requirements.
“You can combine these superconductors with these magnetic materials and
potentially make novel devices where you could use an external magnetic field to
switch these devices,” Gupta said.
Chromium dioxide is a material that was used for decades in producing both high
quality audio and videotapes, Gupta said.
“We were one of the first to make high-quality thin films,” Gupta said of UA’s
MINT Center. “Thin films are difficult to produce. If you don’t use the proper
conditions you will produce a different material that does not have these unique
properties.
The discovery could also assist researchers in their efforts to bring MRAM, a
new type of experimental computer memory, to market. Unlike today’s standard
memory, MRAM requires no extensive boot-up process and uses less power than
conventional memory. It is also non-volatile, so if there’s a sudden power
outage it would “remember” its state, preventing the computer user from losing
data. Sensors, known as magnetic tunnel junction devices, are essential
components in devices that might one day feature this next generation of
computer memory.
The announcement in the Nature article could be another step toward making MRAM
a reality for the average computer user.
“If we are able to expand this and make magnetic tunnel junction devices, you
will see extremely large changes in resistance,” Gupta said.
The experiments announced in Nature were performed under extremely low
temperature conditions. Temperatures much lower than room temperature are the
only known conditions under which superconductors provide no resistance. Gupta
says achieving similar results under room temperature conditions would be
industry-altering.
“That is still the holy grail.”
Funding for UA’s portion of the research was provided to MINT by the National
Science Foundation. UA’s MINT center is a multi-disciplinary research program
focusing on information storage, including magnetic data storage. It was
selected by the National Science Foundation as one of the 29 Materials Research
and Science and Engineering Centers in the United States. MINT has continuously
carried this designation since it first achieved it in 1994 as one of the 11
centers so recognized in the agency’s original selection.
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