|Physicists create first "spin dynamo"|
|Posted Tuesday, April 17, 2007 2:15 PM|
|(Left) XuezhiZhou, Gwyn Williams, Can-Ming Hu, Nikolai Mechking and Yongsheng Gui,|
Thanks to advances in nanotechnology and microelectronics, we can now make complex devices that are invisible to the naked eye. A major challenge is finding a way to power these tiny systems, and a team of University of Manitoba researchers may have found an answer.
Based in the department of physics and astronomy, the group has created a microscopic device that can convert microwave energy into electrical current. Called a “spin dynamo,” it generates current from the spin of electrons, rather than their charge, and it represents a major leap forward in our understanding of spin dynamics and magnetism.
Led by Can-Ming Hu, the team includes physics professor Gwyn Williams, research associates Yongsheng Gui and Xuezhi Zhou, and Nikolai Mecking, a visiting PhD student from the University of Hamburg.
The team’s findings were published in the March 9 edition of Physical Review Letters, the journal of the American Physical Society.
Hu said most of the electrical current we use everyday is produced by dynamos based on a principle first demonstrated by English physicist Michael Faraday in 1831. Faraday’s dynamo produced electrical current by rotating a copper disk inside a magnetic field.
“Electrons are charged particles, and when the copper plate is rotated in the magnetic field, electrons are deflected off, resulting in current,” Hu said.
Unlike Faraday’s model, the new spin dynamo produces current from the rotation of the electrons themselves. The process still involves placing a piece of metal in a magnetic field, but the metal does not move. The spin dynamo can also be made very small.
“In our case, the metallic plate is actually a ferromagnetic strip that is thinner than a human hair,” Hu said. “When we expose them to microwaves, the electrons on the strip dance like little tops, behaviour we call ‘spin precession,’ and in the magnetic field, this spin precession produces electrical current.”
Hu’s team has shown that it is possible to produce electrical current from electron spin, and that microwave energy is all that is needed. In theory, Hu said, this principle could be refined to the point where it might one day be possible to generate electrical current from the ambient microwaves that are all around us as a result of modern communications technology.
Hu said there is still a lot of work to be done before the new device could be used as a power source in practical applications. In the meantime, though, the spin dynamo will be a valuable tool for studying the nature of spin precession.
“Understanding electron spin is a fundamental question related to the origin of magnets, or why a compass is a compass,” Hu said. “By measuring current, this device will give us a new way to detect electron spin, which is very exciting indeed.”
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