New class of "non-Joulian magnets" have potential to revolutionize electronics
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 175years ago, physicist James Prescott Joule (the same person after which theunit of work energy, the joule, is named) discovered magnetostriction, where iron-basedmagnetic materials minutely distort in shape, but not in volume, when placed in a magnetic field. Since then, it hasbeen pretty much accepted that this was the way all magnetic materials behaved.
The workconducted on iron alloys (including iron-gallium, iron-germanium, and iron-aluminum) by researchers at UMD and Temple, however, has resultedin the observation of a property never before encountered in magnetic materials: a change in volume whilst in the process of magnetization. As this wasfundamentally different to the phenomenon discovered by Joule, the new magnets are called "non-Joulian magnets."
"Ourfindings fundamentally change the way we think about a certain type ofmagnetism that has been in place since 1841," said former Ph.D. studentHarsh Deep Chopra, now professor and chair of mechanical engineering at TempleUniversity. "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 toharvest or convert energy with minimal heat loss."
The researchers say the low-energy characteristics of these new magnets means they show potential for the production ofsmaller, more efficient sensors and actuators with ever-smaller heatsignatures. Other potential applications range from efficient energy-harvesting devices and compactmicro-actuators for space, automotive, robotics and medical applications, through to actuators with exceptionally low thermal signatures ideal for defenseapplications.
To createthese new magnetic materials, professor of materials science and engineering ManfredWuttig, and Chopra heated certain iron-based alloys in afurnace to approximately 760º C (1,400º F) for 30 minutes, then quickly cooledthem to room temperature. Once cooled, the new materials demonstrated thenon-Joulian behavior.
Instudying the newly-formed materials under a microscope, the team was astoundedto find tiny cell-like structures that appeared to be responsiblefor the strange non-Joulian magnetostriction they observed.
"Theresponse of these magnets differs fundamentally from that likely envisioned byJoule,” said professor Wuttig. "He must have thought that magnets respond in a uniformfashion. Knowing about this unique structure will enable researchers to developnew materials with similarly attractive properties."
Thoughthis research is in its infancy, the researchers say there is great potential for the production ofmulti-pole magnets created from simple, abundant alloys to replace expensive rare-earthelement magnets in all manner of applications.
The resultsof this research were recently published in the journal Nature.
Source:University of Maryland