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Posted: Jan 25, 2006
Nanomagnetism findings point to new computer technologies based on magnetic spin
(Nanowerk News) An unusual pool of scientific
talent at the U.S. Department of Energy's Argonne National Laboratory, combined
with new nanofabrication and nanocharacterization instruments, is helping
to open a new frontier in electronics, to be made up of very small and very
A new discovery by this group opens a path to new computer technologies and
related devices, and could drive entire industries into the future, the researchers
The researchers learned that swirling spin structures called magnetic vortices,
when trapped within lithographically patterned ferromagnetic structures, behave
in novel ways. In a nickel-iron alloy, the two vortices swirl in opposite directions,
one clockwise and the other counterclockwise. However, the researchers discovered
that the magnetic polarity of the central core of the vortices, like the eye
of a hurricane, controlled the time-evolution of the magnetic properties, not
the swirling direction. The research was reported in the new peer-reviewed journalNature
Physics Dec. 1, 2005 issue.
The material being studied is about one micron in size, and the area of the
vortex core is about 10 nanometers in size. For comparison, the period at the
end of this sentence is about 100 microns or 100,000 nanometers in
Argonne researcher Sam Bader with a new instrument to measure spin resonance frequencies, developed by Argonne senior scientist Frank Fradin. (Source: Argonne National Laboratory)
Group leader Sam Bader, an Argonne scientist for more than 30 years, explained
that the work could lead to the next generation of electronic devices. “When
the first computer hard disk was introduced 50 years ago, it required a rather
large size to store each bit of digital information. On today's computer disks,
the corresponding size is about one-50-millionth of that needed in the original
disks. We are now moving well into the nanoscale range, and nanomagnetism is
one of the real drivers of the nanotechnology field.”
The beauty of nanoscience, Bader said, is that researchers can take conventional
materials, such as the nickel-iron alloy, reduce them to the nanoscale and
create whole new properties. "Thinking far into the future, for example, we
can envision circuits where the flow of spin, not the flow of electrical charge,
will operate computers and other electronic devices while saving wasted heat
energy that is generated in present-day devices."
As with other materials at the nanoscale, Bader said, nanomagnets take on
new properties, some of them unpredictable.
Understanding that unpredictability and underlying physics is important to
researchers developing the new technology, said Argonne scientist Val Novosad. "With
this very small array of spins, where each atom has a magnetic moment, the
vortex core responds to stimuli by traveling in spiral trajectories."
The researchers created the material in the form of an array of elliptical
pancakes, each holding two vortex cores, stimulated the material with a magnetic
pulse and watched the subsequent behavior.
"This first-ever reported experiment revealing unique dynamic behavior of
two interacting magnetic vortices required a considerable assist from technology," Novosad
Argonne senior scientist Marcos Grimsditch provided the inspiration for the
novel magnetic configuration of the samples, which were fabricated using a
new electron beam lithography facility to be housed at Argonne 's Center
for Nanoscale Materials, scheduled to open later this year. The tiny process
could be monitored using a new instrument to measure spin resonance frequencies,
developed by Argonne senior scientist Frank Fradin. And the interpretation
of the experimental data was assisted by numerical modeling from Argonne post-doctoral
student Kristen Buchanan, winner of a fellowship from Canada 's Natural
Science and Engineering Research Council, and the analytical theory expertise
of visiting theorist Konstantin Guslienko at Argonne's Theory Institute.
"Every step along the way was state of the art," Bader said, "from the fabrication
of the material to the measurement of the spin to the creation of software
to illustrate the data through a movie."
Source: Argonne National Laboratory
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