Domain walls that conduct electricity( BERKELEY CA The logic and memory fu...)

BERKELEY, CA The logic and memory functions of future electronic devices could shrink dramatically to one or two nanometers (billionths of a meter) instead of the many tens of nanometers that characterize today's most advanced elements - if a way can be found to control domain walls, the ultrathin transition zones that separate regions of a material having different magnetic, electric, or other properties.

In a material called bismuth ferrite, an unusual compound of bismuth, iron, and oxygen (BiFe03), scientists at the Department of Energy's Lawrence Berkeley National Laboratory and the University of California at Berkeley have discovered a property of domain walls never seen before. Although bismuth ferrite is an insulator, the researchers found that between domains having different electrical polarization, the domain walls themselves just two nanometers wide conduct electricity at room temperature.

"A domain wall is virtually a two-dimensional sheet through the material," says Ramamoorthy Ramesh of Berkeley Lab's Materials Sciences Division (MSD), a professor in the Department of Materials Science and Engineering and the Department of Physics at UC Berkeley. "Because they are so small and can be moved, domain walls have great promise for future electronics."

Ramesh heads MSD's Quantum Materials program for the study of complex materials, which is supported by the Office of Basic Energy Sciences (BES) within the Department of Energy's Office of Science. Unlike familiar metals or semiconductors, the basic electrical and magnetic properties of complex materials are extremely sensitive to their environment, says Ramesh. "Materials called multiferroics are an example of this kind of material, and bismuth ferrite is a prototypical multiferroic."

The promise of multiferroics

Multiferroics may be an unfamiliar term, but is not likely to remain so for long. It describes materials that simultaneously exhi
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