Prospect and status of iron-based rare-earth-free permanent magnetic materials

With the advent of high performance permanent magnets based on the rare-earth (RE) elements such as Sm-Co, Nd-Fe-B alloys in 1980s, the application areas have been extended from the electronics to hybrid electric vehicles and wind turbines etc. However, the advantages of these RE based magnets may be overshadowed by the supply constraints, high prices and environmental issues. Much attention has been paid on non-RE element based permanent magnetic materials as next generation of permanent magnetic materials, due to low cost, large coercivity and high Curie temperatures (working temperatures). A variety of methods are available to manufacture RE-free permanent magnetic materials in bulk, nanostructure, nanocomposite and thin films. The proper scale-up methods to produce magnetic nanostructures with high energy efficiency have still been a significant challenge, which are very important to the development of novel RE-free permanent magnetic materials to meet tomorrow's energy needs. In this review paper, we emphasize to introduce the prospect and status of developments of iron-based RE-free hard-magnetic nanomaterials involving magnetic thin films, nanocomposites and nanostructures.