Magnets are at the heart of much of our technology, and their properties are exploited in a myriad ways across a vast range of devices, from simple relays to enormously complex particle accelerators. A new class of magnets discovered by scientists at the University of Maryland (UMD) and Temple University may lead to other types of magnets that expand in different ways, with multiple, cellular magnetic fields, and possibly give rise to a host of new devices. The team also believes that these new magnets could replace expensive, rare-earth magnets with ones made of abundant metal alloys.

About 175 years ago, physicist James Prescott Joule (the same person after which the unit of work energy, the joule, is named) discovered magnetostriction, where iron-based magnetic materials minutely distort in shape, but not in volume, when placed in a magnetic field. Since then, it has been pretty much accepted that this was the way all magnetic materials behaved.

The work conducted on iron alloys (including iron-gallium, iron-germanium, and iron-aluminum) by researchers at UMD and Temple, however, has resulted in the observation of a property never before encountered in magnetic materials: a change in volume whilst in the process of magnetization. As this was fundamentally different to the phenomenon discovered by Joule, the new magnets are called "non-Joulian magnets."

"Our findings fundamentally change the way we think about a certain type of magnetism that has been in place since 1841," said former Ph.D. student Harsh Deep Chopra, now professor and chair of mechanical engineering at Temple University. "We have discovered a new class of magnets, which we call 'Non-Joulian Magnets', that show a large volume change in magnetic fields. Moreover, these non-Joulian magnets also possess the remarkable ability to harvest or convert energy with minimal heat loss."