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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, "Non-Joulian Magnetostriction," in the May 21st issue of the journal, Nature (DOI:10.1038/nature14459).
"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."
"The response of these magnets differs fundamentally from that likely envisioned by Joule," said Wuttig. "He must have thought that magnets respond in a uniform fashion."
Chopra and Wuttig discovered that when they thermally treated certain iron-based alloys by heating them in a furnace at approximately 760 degrees Celsius for 30 minutes, then rapidly cooled them to room temperature, the materials exhibited the non-Joulian behavior.
The researchers found the thermally treated materials contained never before seen microscopic cellular-like structures whose response to a magnetic field is at the heart of non-Joulian magnetostriction. "Knowing about this unique structure will enable researchers to develop new materials with similarly attractive properties," Wuttig added.
The researchers noted that conventional magnets can only be used as actuators for exerting forces in one direction since they are limited by Joule magnetostriction. Actuation, even in two directions, requires bulky stacks of magnets, which increase size and reduce efficiency. Since non-Joulian magnets spontaneously expand in all directions, compact omnidirectional actuators can now be easily realized, they said.
Because these new magnets also have energy efficient characteristics, they can be used to create a new generation of sensors and actuators with vanishingly small heat signatures, said the researchers. These magnets could also find applications in efficient energy harvesting devices; compact micro-actuators for aerospace, automobile, biomedical, space and robotics applications; and ultra-low thermal signature actuators for sonars and defense applications.
An actuator is a type of motor that is responsible for moving or controlling a mechanism or system.
It is operated by a source of energy, typically electric current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input.
by heating them in a furnace at approximately 760 degrees Celsius for 30 minutes, then rapidly cooled them to room temperature
The article talked about onmidirectional actuators, not omnidirectional magnets.
originally posted by: MysterX
Since non-Joulian magnets spontaneously expand in all directions, compact omnidirectional actuators can now be easily realized
originally posted by: MysterX
Omnidirectional magnets...and to think they said a magnet based overunity device was impossible.
originally posted by: Kashai
a reply to: pheonix358
I would say that one would have a sword that could carry an electrical charge in a rather efficient way as long as one had the precise formula for the "iron based alloys".
originally posted by: cavtrooper7
Wouldn't this aid Gauss weapon systems as well?,perhaps magnetic containmemt of anti matter?
I was looking for some indication of the amount in the article but if it's there I didn't see it. How much is "not a huge amount"? 10% change in volume?
originally posted by: Bedlam
It's a material that changes volume as well as shape in a magnetic field. Not a huge amount, though.
The 180 degree Bloch walls oriented along a magnetically easy direction generate the demagnetized state of a thin circular ferromagnetic plate, Extended Data Fig. 5a. If the magnetostriction of the material equals zero the Bloch walls may be considered laminates of two 90 degree walls.
Therefore, the spontaneous magnetization at the center of the 180 degree walls is directed normal to the walls. This fact is of little consequence as long as λ100≪1. However, it becomes significant if λ100 is finite as it does in the Fe-Ga, Al, Ge family. In this case, a significant stress arises in the center of the 180 degree Bloch walls causing the crystal to twin thereby forming the state we discovered.