Magnetism and Microstructure: The Role of Interfaces

The role of microstructure in determining the magnetic properties of materials is introduced and the role of interfaces, including intergranular phases, is presented in the context of three different classes of materials exhibiting novel magnetic behavior. This includes perpendicular interface anisotropy in metallic multilayers, origin of coercivity in hard magnets and the role of interface roughening in giant magnetoresistive materials. It is demonstrated that in these systems the microstructure of the interfaces (structural and compositional roughness, compound formation, strain and defects) and intergranular coupling and/or isolation are the appropriate length scales that determine their magnetic and magnetotransport properties. This approach not only makes it possible to atomically engineer thin films and nanostructures but also offers opportunities to elucidate the physics of magnetism and build new materials with unique properties.