Rare Coupling Of Magnetic and Electric Properties İn A Single Material

Researchers at the U.S. Department of Energy's Brookhaven National Laboratory have observed a new way that magnetic and electric properties — which have a long history of ignoring and counteracting each other — can coexist in a special class of metals. These materials, known as multiferroics, could serve as the basis for the next generation of faster and energy-efficient logic, memory, and sensing technology. The researchers, who worked with colleagues at the Leibniz Institute for Solid State and Materials Research in Germany, published their findings in the July 25, 2011, edition of Physical Review Letters.

Ferromagnets are materials that display a permanent magnetic moment, or magnetic direction, similar to how a compass needle always points north. They assist in a variety of daily tasks, from sticking a reminder to the fridge door to storing information on a computer's hard drive. Ferroelectrics are materials that display a permanent electric polarization — a set direction of charge — and respond to the application of an electric field by switching this direction. They are commonly used in applications like sonar, medical imaging, and sensors.

"In principle, the coupling of an ordered magnetic material with an ordered electric material could lead to very useful devices," said Brookhaven physicist Stuart Wilkins, one of the paper's authors. "For instance, one could imagine a device in which information is written by application of an electric field and read by detecting its magnetic state. This would make a faster and much more energy-efficient data storage device than is available today."

But multiferroics — magnetic materials with north and south poles that can be reversed with an electric field — are rare in nature. Ferroelectricity and magnetism tend to be mutually exclusive and interact weakly with each other when they coexist.

Most models used by physicists to describe this coupling are based on the idea of distorting the atomic arrangement, or crystal lattice, of a magnetic material, which can result in an electric polarization.