High performance magnets: which properties? which prospects?
In this paper we will recall the fundamentals of permanent magnetism, and outline the essential link between extrinsic properties and microstructure. We will describe the evolution in the properties of permanent magnets over the last century, linking the spectacular improvements achieved with the discovery of new phases and the development of improved processing.
We will explain the present dependence on the use of heavy rare earth elements such as Dy and Tb, in the production of Nd-Fe-B based magnets suitable for operation at the relatively high working temperatures of the motors and generators used in clean energy conversion (below 180°C).
We will discuss prospects for the development of heavy rare earth free Nd-Fe-B magnets, based on recent results from literature, and our own work on model thick film structures.
Finally, we will outline expected future developments of both rare earth containing and rare earth free high performance permanent magnets.
By Dr. Nora Dempsey, CNRS Grenoble.