Smarter use of rare earths

David Kramer’s report about China’s rare-earths dominance (Physics Today, May 2010, page 22 ), caught my interest. Our collective US ignorance about the rare earths and magnets is causing us to overlook one important area as we try to find a national strategy for securing rare earths and any raw material that is not being produced domestically.

For the past 25 years or so, the rare-earth element dysprosium has been added to neodymium iron boron magnets to increase their resistance to demagnetization. Historically, the improvement came at a relatively low cost, so most designs used a bit of extra dysprosium as a safety factor. The resultant overuse of dysprosium has forced up its price to the point where it may be harder to acquire than neodymium.

Trying to find new materials is all well and good, but we should devote a comparable amount of energy to being smarter with what we already have. For example, NdFeB magnets in hard disk drives over the past couple of decades have decreased in size with each succeeding generation. Although a small part of the change is that magnet properties have gradually improved, the primary reason for the reduction is that engineers have learned how to do more with less material. The same effect will occur with hybrid vehicles and wind turbines; it is inevitable.

If we were smarter about our use of magnets—in materials selection, design, and recycling—we would be in a much better position on rare earths than we are today.