Perpendicular magnetic anisotropy of CoPt-TiO2 composite film with nano-fiber structure

Co-Pt-Ti-O films were prepared by sputtering a Co-Pt-Ti composite target in Ar+O2 atmosphere. Upon thermal anneal at elevated temperatures, fcc-CoPt and TiO2 are formed in the film as a separated phase from one other. Both phases develop as the fiber-like columnar grains of less than 10 nm in their lateral size, and are distributed separately from each other. The film does not show perpendicular magnetic anisotropy unless it is thicker than approximately 50 nm, which is explained in terms of strong shape anisotropy of magnetic CoPt nano-fibers vertical to the substrate. The TiO2 in the film plays a role to separate CoPt nano-fibers from one another and to reduce their mutual magnetic interaction. The nano-scale nature and perpendicular magnetic anisotropy of the CoPt-TiO2 film make it a very promising candidate for future recording media with ultra-high area density.