Crystallographic orientation control in L1₀ FePt films on CrRu underlayer

L1₀ ordered FePt films of (200) or (001) preferred orientations with longitudinal or perpendicular anisotropy have been prepared by DC magnetron sputtering. The fct-FePt film exhibits (200) preferred orientation at the base pressure of 4×10^-6 Torr. As the base pressure is decreased (below 9×10^-7 Torr), the fct-FePt films exhibit (001) preferred orientation. When the CrRu underlayer thickness decreases from 80 to 30 nm, an improved CrRu (002) and fct-FePt (001) orientation is obtained. Ag doping in FePt film also promotes the growth of fct-FePt (200) orientation and suppresses the growth of fct-FePt (001) orientation. As the thickness of CrRu underlayer decreases to 15 and 8 nm, the orientation of CrRu (002) deteriorates, and FePt-Ag composite films with an improved fct (200) orientation were obtained. It is considered that the changes in relative surface energy due to the introduction of atmospheric components, Ag doping and epitaxial growth energy arising from the lattice misfit between FePt films and CrRu underlayer play an important role in controlling the crystallographic orientation of FePt films on the CrRu underlayer.