Many advances in magnetic materials have resulted from the ability to structure materials on an appropriate magnetic length strip. This is typically the exchange length or the domain wall width of a hard phase, but in either case the characteristic length scale is a few nanometers. As the dimensions of the grains in a magnetic nanostructure approach this limit, the magnetic properties become significantly different from those in bulk. More specifically, nanostructured materials significantly extend the range of available magnetic properties. A variety of materials processing issues centers on the need to control nucleation and crystal growth on a very small length scale. Additional issues focus on the nature of the grain boundaries and the exchange coupling across them. This book provides a comprehensive overview of developments in the field. Topics include: permanent magnet processing; intrinsic properties of permanent magnetic materials; nanoscale hard magnetism; permanent magnet applications; microstructure and micromagnetics; thin-film permanent magnets; fine-particle magnets; nanocrystalline antiferro- and ferrimagnets; ultrasoft nanocrystalline and amorphous materials and nanocrystalline magnetic thin films.