Pattern of magnetic squares showing
two distinct polarities in black and white;
© Brookhaven National Laboratory
"The smaller space one bit of information can occupy, the more data you can get into a device and the faster it can operate," says Yimei Zhu, a senior scientist at the U.S. Department of Energy's Brookhaven National Laboratory. His group has fabricated patterned magnetic films by depositing magnetic materials such as Permalloy and cobalt in patterns of dots, squares, or ellipses across a surface of nonmagnetic substrates such as carbon or silicon nitride. With each dot measuring about 100 nanometers, or billionths of a meter across, these materials could serve as building blocks for new nanoscale magneto-electronic devices and data storage media.
"For digital communication and data storage applications you need two stable states to encode the 'ones' and 'zeros' of digital information," Zhu explains. In his array of magnetic dots, the two states are the two distinct spin orientations, or polarities, of the dots' internal magnetic fields.
Using a field-emission transmission electron microscope equipped with a custom-made objective lens, Zhu's group can probe the magnetic properties of each dot, and map how the spins "flip" in response to an external magnetic field, or other variables such as temperature, environment, and crystal defects.
"What we are looking for is two very stable states with a well-defined switching mechanism," Zhu says. Such a medium could be encoded with digital data by switching the spins from "up" to "down", or clockwise to counter clockwise, at will.
"In order to make these materials into useful, practical magnetic building blocks, we really have to understand this switching, or reversal, mechanism," Zhu says. Once the researchers understand the mechanism, scientists may be able to scale the materials down even smaller, perhaps to the molecular scale.
COMPAMED.de; Source: Brookhaven National Laboratory