Exchange-spring permanent magnets: Great Expectations or an Odyssey?
Jeff Shield
Department of Mechanical Engineering
University of Nebraska
The magnetic properties of modern high-energy permanent magnets are critically
dependent on microstructural features such as grain size, morphology, and phase content.
The most promising class of permanent magnets to come along in recent years is
exchange-spring magnets that combine hard and soft magnetic materials on the
nanoscale. Great advancements in the energy density of permanent magnets have been
predicted. However, these great expectations have not been realized. In our work, we
are attempting to rectify this in a number of ways. For one, we are attempting to better
understand the magnetic reversal processes that occur in exchange-spring permanent
magnets. Then, microstructures that better resist demagnetization can be designed.
Secondly, we are attempting to construct “perfect” nanocomposite permanent magnets.
These include “atom-up” approaches such as cluster beam fabrication techniques, and
more traditional processing involving rapid solidification and alloy development. This
talk will summarize our odyssey involving exchange-spring magnets.