Perpendicular magnetic anisotropy of Co–TiN composite film with nano-fiber structure

Abstract

Co–Ti–N films have been prepared by sputter deposition of Co and Ti in Ar+N2 atmosphere. Upon thermal anneal at elevated temperatures, Co (face-centered cubic) and TiN were formed in the film and separated from each other. Fiber-like microstructure developed with Co nano-fibers vertical to the substrate surface, and with their lateral size being less than 10 nm. The magnetic anisotropy of such films depends strongly on the film thickness. The Co–TiN films with their thickness above 100 nm show perpendicular magnetic anisotropy, which is explained in terms of shape anisotropy. Considering their microstructure, it is concluded that the diameter to length ratio of Co nano-fibers is an important factor controlling the magnetic anisotropy. For the Co–TiN film to show perpendicular magnetic anisotropy, the diameter to length ratio has to be smaller than 0.07 according to the experimental results. TiN in the films plays an important role in separating Co nano-fibers and thus to reduce the lateral magnetic interaction among them. The nano-scale nature and perpendicular magnetic anisotropy of the Co–TiN nanocomposite film make it a very promising candidate for future ultrahigh magnetic recording media.