The swirling field of a magnet—rendered visible by a sprinkling of iron filings—emerges from the microscopic behavior of atoms and their electrons. In permanent magnets, neighboring atoms align and lock into place to create inseparable north and south poles. For other materials, magnetism can be induced by a field strong enough to coax atoms into alignment.
In both cases, atoms are typically arranged in the rigid structure of a solid, glued into a grid and prevented from moving. But the team of JQI Fellow Ian Spielman has been studying the magnetic properties of systems whose tiny constituents are free to roam around—a phenomenon called “itinerant magnetism."
“When we think of magnets, we usually think of some lattice,” says graduate student Ana Valdés-Curiel. Now, in a new experiment, Valdés-Curiel and her colleagues have seen the signatures of itinerant magnetism arise in a cold cloud of rubidium atoms.
The team mapped out the magnetic properties of their atomic cloud, probing the transition between unmagnetized and magnetized phases. Using interfering lasers, the researchers dialed in magnetic fields and observed the atoms’ responses. The experiment, which was the first to directly observe magnetic properties that result from the particles’ motion, was reported March 30 in Nature Communications. Read More