A new closeup of the cell-like structure formed by the molecules of the iron alloy after baking and super-cooling. Photo by Harsh Deep Chopra/Temple University
PHILADELPHIA, May 20 (UPI) -- Researchers have discovered a new class of magnets that swell when placed in a magnetic field and have a small heat signature, attributes that scientists believe will make a variety of energy-harvesting devices more efficient.
Until now, it was assumed iron-based magnets could only change shape, not volume. It's a principle -- first described in the 1840s by physicist James Prescott Joule -- called "Joule Magnetostriction." The principle describes all magnetic materials used today. These limitations make magnets one-directional, able to exert a force in a only a single direction. This limits their efficiency when employed as actuaries in energy harvesting devices and other technologies.
But new research by scientists at Temple University and University of Maryland suggests a new type of magnetic material can change shape and volume -- making them omnidirectional -- and can transfer energy without generating much heat.
"We have discovered a new class of magnets, which we call 'Non-Joulian Magnets,' that show a large volume change in magnetic fields," Harsh Deep Chopra, professor and chair of mechanical engineering at Temple, explained in press release. "Moreover, these non-Joulian magnets also possess the remarkable ability to harvest or convert energy with minimal heat loss."
Chopra and his research partner, Manfred Wuttig, a material scientist at Maryland, discovered the new magnetic material after baking iron-based alloys in an oven at 1,400 degrees Fahrenheit for 30 minutes, before rapidly cooling them. The process changed the organization of the magnets' molecules, creating a organized, cell-like structure, and altered the way they responded to magnetic energy.
These omnidirectional magnets could be used as sensors and actuators, and find a range of applications in aerospace, automobile, biomedical, space and robotics fields.
"Chopra and Wuttig's work is a good example of how basic research advances can be true game changers," said Tomasz Durakiewicz, director of the condensed matter physics program at the National Science Foundation, which provided funding for the study. "Their probing of generally accepted tenets about magnetism has led to a new understanding of an old paradigm. This research has the potential to catapult sustainable, energy-efficient materials in a very wide range of applications."
The new research is published in the journal Nature.
