Researchers show that heat and sound can be controlled with magnets

For the first time, researchers have shown that both heat and sound can be controlled with magnets. Although it is not well known, outside of the world of physics, heat and sound are transmitted by the same particles. Phonons, the cousin of the light transmitting photon, carry both.

“Essentially, heat is the vibration of atoms. 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,” said Joseph Heremans, Ohio Eminent Scholar in Nanotechnology and professor of mechanical engineering at Ohio State in a statement.

In a new paper, published in the journal Nature Materials, researchers demonstrated that the heat flowing through a semiconductor cab be reduced by 12 percent using a magnetic field the size of a medical MIR.

“This adds a new dimension to our understanding of acoustic waves. We’ve shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too,” said Heremans.

According to the researchers, the manipulation of heat was achieved because of a quirk in the behavior of the semiconductor at very low temperatures. The experiment involved a peculiar tuning fork, with one arm 1 mm wide and one 4 mm wide. Heaters were placed at the base of each arm.

In the absence of the magnetic field, heat behaved as it is expected to with the wider arm transferring more energy.

“Imagine that the tuning fork is a track, and the phonons flowing up from the base are runners on the track. The runners who take the narrow side of the fork barely have enough room to squeeze through, and they keep bumping into the walls of the track, which slows them down. The runners who take the wider track can run faster, because they have lots of room. All of them end up passing through the material–the question is how fast. The more collisions they undergo, the slower they go,” said Heremans

However, with a powerful magnetic field turned on, heat flow through the larger arm dropped by 12 percent.

While the ability to control the flow of heat and sound has a wide variety of potential applications including the storage of heat for later use and more effective control of energy systems, none of these are likely to be achieved anytime soon.

At present 7-tesla magnets, such as the one used in the study, are currently only used in laboratories and hospitals. Additionally in order to control the heat flow, the “tuning fork” of semiconductor material, had to be cooled to -450 degrees Fahrenheit (-268 degrees Celsius) which is close to absolute zero. In order to have any practical application outside of the lab, these conditions would have to be met inexpensively enough to make the heat transfer economically beneficial.

Hermans, however, told Newsweek that he thinks the effect can be reproduced at room temperature which is the next step in his research.

 

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