Scientists have observed magnetic properties typically associated with those observed in rare-earth elements in iron.
The discovery opens the possibility of using iron to provide both the magnetism and permanence in high-strength permanent magnets, like those used in direct-drive wind turbines or electric motors in hybrid cars, researchers said.
Scientists at the US Department of Energy's Ames Laboratory observed the properties in a new iron based compound that does not contain rare earth elements, when the iron atom is positioned between two nitrogen atoms.
In modern magnets, iron gives magnets their strength, and comes with the benefits of being abundant and cheap.
But the magnet recipe must also include rare earth elements, which lend magnets "permanence", or the ability to keep the direction of the magnetic field fixed (also called anisotropy).
The challenge is rare-earths materials are expensive and at risk of domestic supply shortages. So, ideal next-generation permanent magnets will rely more heavily on iron or other abundant materials and less on rare earths.
"The breakthrough here is that we see magnetic anisotropy normally associated with rare earths ions in iron," said Paul Canfield, Ames Laboratory physicist.
"This isn't an industrial breakthrough at this point because these magnetic properties only reveal themselves at cryogenic temperatures. But, it's a basic science breakthrough that hopefully will point the way to future technical breakthroughs," he said.
Canfield and his colleagues, including postdoctoral research associate Anton Jesche, designed a new technique to grow lithium-iron-nitride single crystals from a lithium-nitrogen solution.
"Using nitrogen in solution growth had not yet been well explored because, since we typically think of nitrogen as a gas, it's challenging to get into a solution," said Jesche.
"But we found that lithium - lightest solid element - looked like it could hold nitrogen in solution. So, we mixed together lithium and lithium-nitride powder, and it worked. It created a solution," Jesche said.
Then the group added in iron and, to their surprise, the iron dissolved.
"Usually iron and lithium don't mix. It seems adding nitrogen to the lithium in the solution allows iron to go in," said Canfield, who is also a Distinguished Professor of physics and astronomy at Iowa State University.
"With detailed measurements, we saw that these single iron ions are indeed behaving like a single rare-earth ion would," Canfield said.
"We hope this crystal growing technique and this specific material can be a model system for further theoretical study of these rare-earth-like iron ions.
"As it stands, these materials have clear implications on finding rare-earth-free replacements for permanent magnets - and perhaps also may impact data storage and manipulation in quantum computer applications," he said.
