Magnetic heat study attracts new ideas
Research engineers have discovered how to control heat (and possibly sound) with a magnetic field.
The study is the first ever to prove that acoustic phonons - the 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 at Ohio State University.
“We've shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too.”
While it may be surprising that heat and sound have anything to do with each other, Heremans said both are expressions of the same form of energy, quantum-mechanically speaking.
“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. 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.”
Photon is the name given to particles of light, and particles of heat and sound are known as ‘phonons’.
Phonons have not received as much attention as their luminescent cousins, so not as much is known about them beyond their properties of heat and sound.
The new study shows that phonons have magnetic properties, too.
“We believe that these general properties are present in any solid,” said Hyungyu Jin, a postdoctoral researcher at the university.
The engineers say there are some exciting possibilities.
In materials such as glass, stone, plastic - which are not conventionally magnetic - heat can be controlled magnetically, with a powerful enough magnet.
The discovery was made using a magnetic field roughly the size of a medical MRI to reduce the amount of heat flowing through a semiconductor by 12 per cent.
But there probably will not be any practical applications for the discovery any time soon.
7-tesla magnets like the one used in the study do not exist outside of hospitals and laboratories, and the semiconductor had to be chilled to -268 degrees Celsius to make the atoms in the material slow down enough for the phonons' movements to be detectible.
Next, the researchers plan to test whether they can deflect sound waves sideways with magnetic fields.
The study is published in the journal Nature Materials.