Researchers find that magnets can control heat and sound

Researchers find that magnets can control heat and sound

Researchers at The Ohio State University have discovered how to control heat with a magnetic field. In the March 23 issue of the journal Nature Materials, they describe how a magnetic field roughly the size of a medical MRI reduced the amount of heat flowing through a semiconductor by 12 percent.

The study is the first ever to prove that acoustic phonons—the elemental particles that transmit both heat and sound—have magnetic properties. "This adds a new dimension to our understanding of acoustic waves," said Joseph Heremans, Ohio Eminent Scholar in Nanotechnology and professor of mechanical engineering at Ohio State. "We've shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too."


Researchers at The Ohio State University have discovered that heat can be controlled with a magnetic field. Here, study leader Joseph Heremans, Ohio Eminent Scholar in Nanotechnology, holds the material used in the experiment: a piece of indium antimonide semiconductor shaped into a lopsided tuning fork. The wider arm of the fork (left) measures 4 mm wide, and the narrower one (right) measures 1 mm. The researchers were able to slow the movement of heat through the wider arm of the fork using a magnetic field. Credit: Photo by Kevin Fitzsimons, courtesy of The Ohio State University.

People might be surprised enough to learn that heat and sound have anything to do with each other, much less that either can be controlled by magnets, Heremans acknowledged. But both are expressions of the same form of energy, quantum mechanically speaking. So any force that controls one should control the other. "Essentially, heat is the vibration of atoms," he explained. "Heat is conducted through materials by vibrations. The hotter a material is, the faster the atoms vibrate.

"Sound is the vibration of atoms, too," he continued. "It's through vibrations that I talk to you, because my vocal chords compress the air and create vibrations that travel to you, and you pick them up in your ears as sound." The name "phonon" sounds a lot like "photon." That's because researchers consider them to be cousins: Photons are particles of light, and phonons are particles of heat and sound. But researchers have studied photons intensely for a hundred years—ever since Einstein discovered the photoelectric effect. Phonons haven't received as much attention, and so not as much is known about them beyond their properties of heat and sound.

This study shows that phonons have magnetic properties, too.

"We believe that these general properties are present in any solid," said Hyungyu Jin, Ohio State postdoctoral researcher and lead author of the study. The phonons reacted to the magnetic field, so the particles must be sensitive to magnetism, the researchers concluded. Next, they plan to test whether they can deflect sound waves sideways with magnetic fields. (Source: Nature Materials/The Ohio State University).

0 comments :

Post a Comment