New Discovery Could Allow Magnets to Control Heat and Sound

They have described 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 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, professor of mechanical engineering in a paper published in the journal Nature Materials.

"We have shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too," he added.

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.

But both are expressions of the same form of energy so any force that controls one should control the other.

"Essentially, heat is the vibration of atoms. Heat is conducted through materials by vibrations. The hotter a material is, the faster the atoms vibrate," Heremans explained.

Sound is the vibration of atoms, too.

"It is 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," he suggested.

This study shows that phonons have magnetic properties, too. "We believe that these general properties are present in any solid," added Hyungyu Jin, postdoctoral researcher and lead author of the study.

With the new findings, in materials such as glass, stone and plastic, heat can be controlled magnetically if you have a powerful enough magnet.

The effect would go unnoticed in metals, which transmit so much heat via electrons that any heat carried by phonons is negligible by comparison, the authors conclude.