Enhancing the magnetism:
In this atomic force microscopy topography image of a special mixed phase bismuth ferrite sample, red and green shaded areas indicate two sets of mixed phase regions oriented at 90 degrees to each other. Credit: Image from Ramesh group
(PhysOrg.com) -- Berkeley researchers find enhanced and controllable magnetization in unique bismuth ferrite films.
"The nation that controls magnetism will control the universe," famed fictional detective Dick Tracy predicted back in 1935.
Probably an overstatement, but there's little doubt the nation that leads the development of advanced magnetoelectronic or "spintronic" devices is going to have a serious leg-up on its Information Age competition. A smaller, faster and cheaper way to store and transfer information is the spintronic grand prize and a key to winning this prize is understanding and controlling a multiferroic property known as "spontaneous magnetization."
Now, researchers with the U.S. Department of Energy (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) have been able to enhance spontaneous magnetization in special versions of the popular multiferroic material bismuth ferrite. What's more, they can turn this magnetization "on/off" through the application of an external electric field, a critical ability for the advancement of spintronic technology.
"Taking a novel approach, we've created a new magnetic state in bismuth ferrite along with the ability to electrically control this magnetism at room temperature," says Ramamoorthy Ramesh, a materials scientist with Berkeley Lab's Materials Sciences Division, who led this research. "An enhanced magnetization arises in the rhombohedral phases of our bismuth ferrite self-assembled nanostructures. This magnetization is strain-confined between the tetragonal phases of the material and can be erased by the application of an electric field. The magnetization is restored when the polarity of the electric field is reversed."
Ramesh, who also holds appointments with the University of California Berkeley's Department of Materials Science and Engineering and the Department of Physics, is the corresponding author of a paper in the journal Nature Communications titled "Electrically Controllable Spontaneous Magnetism in Nanoscale Mixed Phase Multiferroics."
Magnetoelectronic or spintronic devices store data through electron spin and its associated magnetic moment rather than the electron charge-based storage of today's electronic devices. Spin, a quantum mechanical property arising from the magnetic moment of a spinning electron, carries a directional value of either "up" or "down" that can be used to encode data in the 0s and 1s of the binary system. In addition to the size, speed and capacity advantages over electronic devices, the data storage in spintronic devices does disappear when the electric current stops.
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