Highly coercive thin-film nanostructures

The processing, structure, and magnetism of highly coercive Sm–Co and FePt thin-film nanostructures are investigated. The structures include 1:5 based Sm–Co–Cu–Ti magnets, particulate FePt:C thin films, and FePt nanotubes. As in other systems, the coercivity depends on texture and imperfections, but there are some additional features. A specific coercivity mechanism in particulate media is a discrete pinning mode intermediate between Stoner–Wohlfarth rotation and ordinary domain-wall pinning. This mechanism yields a coercivity maximum for intermediate intergranular exchange and explains the occurrence of coercivities of 5T in particulate Sm–Co–Cu–Ti magnets.