team of University of Illinois at Chicago electrical
and computer engineers has demonstrated that nanometer-sized
permalloy rings, shaped into tiny rectangles, can
store and access data almost instantly. The finding
brings closer by one step the commercial reality of
a promising form of memory called MRAM.
Access Memory is a contemporary spin on decades-old
core memory technology that uses magnetic fields rather
than electrical charges to reliably store and randomly
memory rings may be the key to making MRAM work.
"With MRAM, you
don't have to refresh the memory," said Vitali
Metlushko, associate professor of electrical and computer
engineering at UIC. "You store it, recall it
and it's there. It's non-volatile."
With the more conventional
DRAM (dynamic random access memory), information is
stored as electrical charges. It must be constantly
refreshed, Metlushko said.
"If your battery
dies, you lose information. But with MRAM, even if
your battery dies, your magnetized layer of memory
stays magnetized and the data stays there, hopefully,
Metlushko and his
graduate students Vidhyashankar Baskaran, Dwarakanath
Geerpuram and Anand Subra Mani report on their research
into square rings used for MRAMs in the October issue
of Nanotechnology, a journal published by the London-based
Institute of Physics.
While Metlushko originally
investigated the memory properties of circular rings,
he found that square and rectangular-shaped rings
sitting on nano-scale memory cells proved to be a
more reliable design for storing data, keeping data
stable and for switching the magnetic field, making
it possible to retrieve information.
But the technology
remains largely in the development phase with improvements
needed in patterning the magnetic material so the
square rings are uniform down at sizes below 50 nanometers.
Presently MRAM square ring cells that work well as
a circuit are comparatively large -- often as big
as 500 nanometers.
determined by shape, and small variations in the shape
of magnetic material leads to drastic changes in switching
properties," said Metlushko. "You want all
of your memory elements, all these MRAM cells, switching
exactly together. We have to be able to control it
The UIC researchers
are part of a larger international team of university
scientists and researchers, as well as researchers
at the Argonne and Los Alamos national laboratories,
among others, trying to advance the state of the art
of nano-scale MRAM. Corporations such as Motorola
and Hitachi also are engaged in substantial MRAM research
Unlike with everyday
DRAM memory chips used in personal computers and other
consumer electronic devices, MRAM holds the promise
of providing instant access memory without the boot-up
delays now common after turning a device's power on.
Also, MRAM is not prone to memory loss caused by radiation
particles, so it may prove to be the memory storage
device of choice in future spacecraft electronics,
such as space probes, launch vehicles, laboratories
and earth-orbiting satellites.
Metlushko said MRAM
is an alternative form of memory that will someday
rank high among low-power nanoelectronic components,
but he said it is hard to predict when.
"Look how much
time it took for the transistor to enter consumer
electronics after its invention. MRAM will happen,
but I wouldn't bet it would be tomorrow. Nanoscience
is unpredictable," he said. "That's part
of the beauty of it."
For more information
about UIC, visit www.uic.edu