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Magnets Can Manipulate Heat and Sound?

Mar 25, 2015 01:42 PM EDT
Pictured: An artist's depiction of a phonon heating solid material. Atoms of the material, shown in orange, are joined with flexible atomic bonds, shown as springs.
(Photo : Renee Ripley, courtesy of The Ohio State University)

New research has found that magnets can manipulate heat and sound, a discovery that can potentially lead to practical applications in the future.

That's at least according to findings published in the journal Nature Materials, in which researchers describe how a magnetic field - roughly the size of a medical MRI - reduced the amount of heat flowing through a semiconductor by 12 percent.

"This adds a new dimension to our understanding of acoustic waves," researcher Joseph Heremans at The Ohio State University said in a statement. "We've shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too."

Not much is known about phonons - particles of heat and sound - because usually their cousins, photons - particles of light - get more attention. So this study is exciting because it's the first ever to prove that acoustic phonons have magnetic properties.

You might not think that heat and sound are similar, but they actually are expressions of the same form of energy, so any force that controls one - like a magnetic field - should control the other.

"Essentially, heat is the vibration of atoms," Heremans 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 added. "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."

Heremans and his colleagues believe that one day heat can be controlled magnetically in solid materials such as glass, stone, plastic that are not normally magnetic. That is, if you have a powerful enough magnet.

However, regrettably there won't be any practical applications of this discovery any time soon, the researchers say. Magnets like the one used in the study (7-tesla) don't exist outside of hospitals and laboratories, and the semiconductor had to be chilled to -450 degrees Fahrenheit (-268 degrees Celsius) in order for the atoms in the material slow down enough for the phonons' movements to be detectible.

Normally, a material's ability to transfer heat would depend solely on the kind of atoms of which it is made. But at very low temperatures, the size of the sample plays an important part as well. That is, a larger sample can transfer heat faster than a smaller sample of the same material.

Though, that does not mean that researchers don't hope that practical applications using magnets' heat and sound manipulating abilities aren't in the future. Next, they plan to test whether they can deflect sound waves sideways with magnetic fields.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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