Alternatives May Reduce Rare Earth Magnets Demand

Rare earth magnets are at the forefront of today's technology from computer hard drives, smart phones to earplugs and electric motors, making varieties of daily necessities getting smaller. While, rare earth elements (REEs) may be difficult to obtain, either because of their scarcity or the challenging geopolitical climate. Recently, scientists have discovered magnets based on rare earths that are more readily available, as well as some promising magnets that do not contain rare earths.

The researchers announced their findings at the American Chemical Society (ACS) 2019 Spring Conference and Expo. The conference contains nearly 13,000 lectures on a wide range of scientific topics. "We have developed new methods to better predict which materials are good magnets," said Dr. Thomas Lograsso, the team leader. " Experimentally, we can 'rehabilitate' near-magnet systems, called paramagnets. We start with alloys or compounds that have all the right properties to be ferromagnetic at room temperature. Many times, these materials have high proportions of iron or cobalt."

Paramagnets are materials that are weakly attracted to a magnetic field and are not permanently magnetized. But by adding alloys, paramagnets have been transformed into ferromagnets, or regular permanent magnets, like the metal surface of a refrigerator. Lograsso's team at the Critical Materials Institute at Ames Laboratory has identified two promising candidates thus far using this "rehabilitative" approach, and both are forms of cerium cobalt: CeCo₃ and CeCo₅. Although cerium is called a rare-earth element, it is very abundant and easy to obtain.

Previous studies on CeCo₃ showed that it exhibited classic paramagnetic behavior. Calculations predicted that by adding magnesium, paramagnetic CeCo₃ could be transformed into a ferromagnet. These predictions have been experimentally validated, Lograsso says, and this property has been observed in measurements of single crystals of the compound.

CeCo₅ is a strong ferromagnetic body. The researchers combined theoretical calculations with high-throughput experiments to zero in on the exact amount of copper and iron to add that would optimize the compound's ferromagnetism. With these additives, the team anticipates that CeCo₅ could someday be used in place of the strongest rare earth magnets that contain neodymium (Nd) and dysprosium (Dy), thus easing demand for those critical elements. Lograsso and colleagues continue to investigate other similar metals that can be added to CeCo₅ to further improve its suitability as a viable substitute for Nd and Dy magnets.

"Replacing rare-earth magnets, which are in high demand, would be ideal, both economically and environmentally," Lograsso says. "Although our modified cerium-cobalt compounds are not as powerful as rare-earth magnets, they could still be highly valuable for certain commercial applications. So, our goal is to match the right magnet material to a specific application -- a so-called 'Goldilocks' non-rare-earth magnet."

To this end, the research group continues to use their strategy to optimize the key characteristics of poor magnets or non-magnets to transform them into alternatives to replace rare earth magnets. For example, they are now using cobalt to optimize the performance of iron germanium, Fe₃Ge. The resulting compound's high magnetization is comparable with the best Nd-based magnets. This strategy is not just limited to Fe₃Ge and is being applied to other promising rare-earth-free compounds to selectively improve magnet properties.

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