Surface roughness and magnetic properties of L1 FePt films on MgO/CrRu/TiN

Processes for making well ordered L1₀ FePt thin films with root-mean-square surface roughness close to 0.4 nm, perpendicular anisotropy greater than 5 kOe and perpendicular squareness near 1 using a deposition temperature of 390 °C have been developed. In this study, we focused on reducing the ordering temperature and smoothness of L1₀ FePt films, while achieving good perpendicular magnetic properties by using MgO/CrRu/TiN or MgO/CrRu/Pt seed layers on Si/SiO₂ substrates. It was found that the chemical ordering of L1₀ FePt films is strongly affected by the insertion of a sputtered MgO seed layer, and the CrRu (002) texture on a (002) textured MgO seed layer is substantially improved at high DC power. In order to prevent Cr diffusion, TiN and Pt films were inserted between the CrRu and FePt films. It was found that the smoothness, L1₀ FePt ordering, and perpendicular magnetic properties were strongly improved by the TiN barrier layer compared to the Pt barrier layer. Increased TiN thickness improved the perpendicular magnetic anisotropy due to the reduced lattice misfit between the CrRu and L1₀ FePt films.