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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, has been discovered by researchers at Temple University and the University of Maryland.
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. This transformative breakthrough has the potential to not only displace existing technologies but create altogether 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. This 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."
[Abstract]: http://www.nature.com/nature/journal/v521/n7552/full/nature14459.html
(Score: 5, Informative) by Covalent on Friday May 22 2015, @02:08AM
Which I don't pretend to fully understand. However, there seems to be a key phrase:
The equilibrium adaptive cellular structure is responsible for long-sought non-dissipative (hysteresis-free), linearly reversible and isotropic magnetization curves along all directions within a single crystal.
It's the "non-dissipative (hysteresis-free)" that's seemingly the big news. I had to look hysteresis up:
"a retardation of an effect when the forces acting upon a body are changed (as if from viscosity or internal friction); especially : a lagging in the values of resulting magnetization in a magnetic material (as iron) due to a changing magnetizing force"
So essentially, these magnets can absorb energy and change shape WITHOUT losing energy to internal friction in the process, and then go back (linearly reversible) to their initial shape and (presumably) release that energy.
This might lead to better generators because (again presumably) current generators lose some energy as the magnets within them change volume and heat up due to hysteresis.
Sounds exciting...if I'm reading it right. Any improvement in energy harvesting / conversion rates would be a big deal indeed.
You can't rationally argue somebody out of a position they didn't rationally get into.
(Score: 3, Informative) by hubie on Friday May 22 2015, @01:40PM
The Editor's summary with the article is a little more approachable:
Your general grasp of the main points of the article, particularly the importance of hysteresis, is spot-on.