Newswise — 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
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.