Magnetism observed in gas for the first time

Sep 17, 2009

(PhysOrg.com) -- For the first time, MIT scientists have observed ferromagnetism in an atomic gas, addressing the decades-old question of whether gases could show properties similar to a magnet made of iron or nickel. Specifically, the team observed the ferromagnetic behavior in a gas of lithium atoms cooled to 150 billionth of 1 Kelvin above absolute zero (-273 degrees C or -459 degrees F).

Team members used the lithium-6 isotope, which consists of three protons, three neutrons and three electrons. Since the number of constituents is odd, lithium-6 is a fermion — a class of exotic particles that have a half-integral spin — and has properties similar to an electron. Therefore, atoms can be used to simulate the behavior of electrons.

For decades, scientists have debated whether it is in principle possible for a or liquid of fermions, which are not in a periodic crystal, to become ferromagnetic.

The MIT research appears to provide a compelling affirmative answer to this question.

"One thing is certain: We have made an important discovery, which will advance our understanding of magnetism," said Ketterle, an MIT physics professor and the corresponding author on the paper. More broadly, magnetic materials have important applications in , nanotechnology and medical diagnostics.

The MIT team trapped a cloud of ultracold lithium atoms in the focus of an infrared . When they gradually increased the repulsive forces between the atoms, they observed several features indicating that the gas has become ferromagnetic.

The cloud first became bigger and then suddenly shrunk. When the atoms were released from the trap, they suddenly expanded faster. This and other observations agreed with theoretical predictions for a phase transition to a ferromagnetic state.

If confirmed, the MIT result may enter the textbooks on magnetism, showing that a gas of fermions does not need a to be ferromagnetic.

"The evidence is pretty strong," said David E. Pritchard, an MIT physics professor and one of the study's authors. "But it is not yet a slam dunk. We were not able to study how the atoms would all point in the same direction. They started to form molecules and may not have had enough time to align themselves."

More information: "Itinerant Ferromagnetism in a Fermi Gas of Ultracold Atoms," Gyu-Boong Jo, Wolfgang Ketterle, et al., Science, Sept. 18, 2009

Provided by Massachusetts Institute of Technology (news : web)

Explore further: Neutrino trident production may offer powerful probe of new physics

add to favorites email to friend print save as pdf

Related Stories

MIT physicists shed new light on superfluidity

Jul 20, 2006

For the first time, MIT scientists have directly observed the transition of a gas to a superfluid, a form of matter closely related to the superconductors that allow electrical currents to travel without resistance.

Physicists create new form of matter

Jun 22, 2005

MIT scientists have brought a supercool end to a heated race among physicists: They have become the first to create a new type of matter, a gas of atoms that shows high-temperature superfluidity. Their wor ...

Ultracold gas mimics ultrahot plasma

Feb 15, 2009

Several years after Duke University researchers announced spectacular behavior of a low density ultracold gas cloud, researchers at Brookhaven National Laboratory have observed strikingly similar properties in a very hot ...

Breaking down superfluidity

Sep 04, 2007

“One of the most exciting areas of research in the last few years has been the realization of the BEC-BCS crossover,” Wolfgang Ketterle tells PhsyOrg.com. Ketterle and a team of scientists at the MIT-Harvard Center for Ul ...

Current theories can't explain observed spin segregation

Oct 16, 2008

(PhysOrg.com) -- Experiments with quantum systems sometimes yield surprising results. This is exactly what happened when John Thomas, a researcher at Duke University in Durham, North Carolina found out when he and his post ...

Recommended for you

How did evolution optimize circadian clocks?

Sep 12, 2014

(Phys.org) —From cyanobacteria to humans, many terrestrial species have acquired circadian rhythms that adapt to sunlight in order to increase survival rates. Studies have shown that the circadian clocks ...

High Flux Isotope Reactor named Nuclear Historic Landmark

Sep 12, 2014

The High Flux Isotope Reactor, or HFIR, now in its 48th year of providing neutrons for research and isotope production at the Department of Energy's Oak Ridge National Laboratory, has been designated a Nuclear ...

User comments : 0