— University of Arkansas physicists have discovered
a new phase in tiny nanodisks and nanorods that potentially
may enable researchers to increase memory storage by
more than one thousand fold. This finding also opens
a new area in physics to fundamental investigation.
Naumov, Laurent Bellaiche and Huaxiang Fu report their
findings in the Dec. 9 issue of the journal Nature.
ordered phase with technological relevance is previously
unknown,” said Naumov, a research scientist who works
with Fu. “The new phase is possible because the nano-size
of the disks wouldn’t allow disorder due to properties
no one has characterized before.”
a new phenomenon. You can think of using it to make
new, hugely increased memories” for storing information,
researchers studied ferroelectric materials at the
nanometer scale. Ferroelectric materials possess spontaneous
dipoles, or charge separations, that allow them to
create the images seen in medical ultrasound and naval
sonar, and also are used to convert signals to sound
in cell phones and other audio devices. How these
dipoles behave when the material is on the nanoscale
is not well known.
“Our goal is to explore the possibility of using a
single nanoparticle to store one data bit,” Naumov
said. However, the net polarization -- which is spontaneously
formed in bulk materials and is so far the key to
storing information -- does not normally exist in
nanoparticles. Naumov, Bellaiche, and Fu decided to
search instead for a new phase in the world of nano-ferroelectrics.
found to their surprise that the dipoles in nanomaterials
form a new state when the temperature is lowered.
The researchers used computer simulations to determine
what happens to the nanorods and nanodiscs when they
reach this state.
found that instead of polarization, the new phase
creates what the researchers call a toroid moment,
which rotates in a circular fashion like a vortex
or a tornado. These moments can rotate in one direction
or another, forming a bi-stable state that is capable
of storing information, like polarization.
the toroid moment provides a different kind of order.
Unlike polarization, the toroid moment can exist in
tiny nanoparticles, which thus allows storage of one
bit of information in a single particle, which has
the advantage of increasing memory density. Also,
unlike the polarization state, in which particles
influence one another if moved in close proximity,
the vortices created by this new phase do not interact
strongly with one another. This means they can be
packed together in a small space.
eliminates the ‘cross-talk’ problem. You can compact
the materials very densely,” Naumov said.
know that in principle this new finding can increase
the memory capacity using nanoparticles, we don't
yet know how long it will take to make a technology
reality,” Fu said. “But it’s a new direction in which
to point people.”