Micromagnetism of hard magnetic nanocrystalline materials

High-quality magnetic materials in general are based on outstanding intrinsic magnetic properties and on special microstructures. Recently, nanocrystalline intermetallic compounds have been proposed as efficient hard magnetic materials with excellent characteristic properties of the hysteresis loop. Nanocrystalline materials can be used to enhance the remanent magnetization by the exchange coupling between the grains. As an example the upper and lower bounds of the remanence and of the coercive field of a nanocrystalline composite material (Nd2Fe14B + alpha-Fe) are discussed on the basis of finite element calculations. If is shown that nanocrystalline composites of hard and soft (alpha-Fe) phases are promising candidates for future permanent magnetic materials.