New class of magnets attract energy harvesting attention

May 22, 2015 // By Paul Buckley
Researchers at Temple University and the University of Maryland have identified a new class of magnets that expand their volume when placed in a magnetic field and generate negligible amounts of wasteful heat during energy harvesting.

The researchers, Harsh Deep Chopra, professor and chair of mechanical engineering at Temple, and Manfred Wuttig, professor of materials science and engineering at Maryland, published their findings in an article entitled 'Non-Joulian Magnetostriction' in the May 21 issue of the journal Nature.

The discovery has the potential to not only displace existing technologies but create new applications due to the unusual combination of magnetic properties.

“Our findings fundamentally change the way we think about a certain type of magnetism that has been in place since 1841,” said Chopra, who also runs the Materials Genomics and Quantum Devices Laboratories at Temple’s College of Engineering.

In the 1840s, physicist James Prescott Joule discovered that iron-based magnetic materials changed their shape but not their volume when placed in a magnetic field. The phenomenon is referred to as 'Joule Magnetostriction', and since its discovery 175 years ago, all magnets have been characterized on this basis.

“We have discovered a new class of magnets, which we call ‘Non-Joulian Magnets,’ that show a large volume change in magnetic fields,” said Chopra. “Moreover, these non-Joulian magnets also possess the remarkable ability to harvest or convert energy with minimal heat loss.”

Never-before-seen highly periodic magnetic ‘cells’ or ‘domains’ in iron-gallium alloys responsible for non-Joulian magnetism.  Image courtesy of Harsh Chopra, Temple University