Powerful Magnets Can Control Both Heat and Sound in Materials

There may be a new technique to control heat with a magnetic field. Researchers have found that a magnetic field roughly the size of a medical MRI can reduce the amount of heat flowing through a semiconductor by 12 percent.

"This adds a new dimension to our understanding of acoustic waves," said Joseph Heremans, one of the researchers, in a news release. "We've shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too."

In fact, this latest study reveals that acoustic phonons, which are the elemental particles that transmit both heat and sound, have magnetic properties.

Both heat and sound are expressions of the same form of energy, quantum mechanically speaking. In theory, any force that controls one should control the other.

"Essentially, heat is the vibration of atoms," said Heremans. "Heat is conducted through materials by vibrations. The hotter a material is, the faster the atoms vibrate. Sound is the vibration of atoms, too. It's through vibrations that I talk to you, because my vocal chords compress the air and create vibrations hat travel to you, and you pick them up in your ears as sound."

The implications are that in materials such as glass, stone and plastic, which are not conventionally magnetic, 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 findings reveal a bit more about phonons and show how they can be impacted by magnetic fields.

The findings are published in the journal Nature Materials.

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