Magnetism observed in gas for the first time

September 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: Ultracold gas mimics ultrahot plasma

Related Stories

Ultracold gas mimics ultrahot plasma

February 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 ...

Recommended for you

Feeling the force between sand grains

August 24, 2016

For the first time, Lawrence Livermore National Laboratory (LLNL) researchers have measured how forces move through 3D granular materials, determining how this important class of materials might pack and behave in processes ...

Spherical tokamak as model for next steps in fusion energy

August 24, 2016

Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility—or "bottle"—that will provide the next steps in the development of fusion reactors. Leading candidates include spherical ...

Funneling fundamental particles

August 24, 2016

Neutrinos are tricky. Although trillions of these harmless, neutral particles pass through us every second, they interact so rarely with matter that, to study them, scientists send a beam of neutrinos to giant detectors. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.