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Physicists observe gas magnetism

PostPosted: October 3rd, 2009, 10:58 pm
by wolfhnd
TORONTO, ON – An international team of physicists has for the first time observed magnetic behaviour in an atomic gas, addressing a decades-old debate as to whether it is possible for a gas or liquid to become ferromagnetic and exhibit magnetic properties.

“Magnets are all around us – holding postcards on the refrigerator, pointing to magnetic north on a compass, and in speakers and headphones – yet some mysteries remain,” says Joseph H. Thywissen, a professor of physics at the University of Toronto and a visiting member of the Massachusetts Institute of Technology-based team leading the research. “We have perhaps found the simplest situation in which permanent magnetism can exist."

The scientists observed the behaviour in a gas of lithium atoms trapped in the focus of an infrared laser beam. The gas was cooled to 150 nK, less than a millionth of a degree above absolute zero, which is at -273 C. When repulsive forces between the atoms were gradually increased, several features indicated that the gas had become ferromagnetic. The cloud first became bigger and then suddenly shrunk, and when the atoms were released from the trap, they suddenly expanded faster. These observations were reported in the 18 Sept 2009 issue of Science, in a paper titled “Itinerant Ferromagnetism in a Fermi Gas of Ultracold Atoms”. ... ism-in-gas