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Rare-earth alloy could slash the cost of motor magnets

07 May, 2015

US researchers have created a new magnetic alloy that, they say, has similar properties to conventional rare-earth magnets but is at least 20–40% cheaper to produce. The material could replace costly high-performance permanent magnets currently used in motors and generators.

The new alloy eliminates the use of one of the scarcest and costliest rare-earth elements, dysprosium, and uses the most abundant rare earth, cerium, instead. The result – an alloy of neodymium, iron and boron co-doped with cerium and cobalt – is said to have comparable properties to traditional sintered magnets containing dysprosium.

Previous attempts to use cerium in rare-earth magnets have failed because it reduces the Curie temperature – the temperature above which an alloy loses its permanent magnet properties. But the researchers at the US Department of Energy’s Ames Laboratory, led by Karl Gschneidner, have now discovered that co-doping the cerium with cobalt allows it to be used without losing the desired magnetic properties.

Experiments performed by researchers Arjun Pathak and Mahmud Khan showed that the cerium-containing alloy’s intrinsic coercivity – its ability to resist demagnetisation – far exceeds that of dysprosium-containing magnets at high temperatures.

“This is quite an exciting result,” says Gschneidner. “We found that this material works better than anything out there at temperatures above 150°C.”

Ames researcher Arjun Pathak arc-melts material used to produce the new magnet

Finding a suitable substitute is key to reducing the current reliance on dysprosium for rare-earth magnets. At present, the demand for dysprosium far outpaces the amount being mined and recycled.

The Ames research has been supported by a US Department of Energy programme aimed at finding cost-effective alternatives to rare-earths.

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