Stacking sequences of the crystallites in Co-Sm films

Abstract

Magnetic thin films sputtered from the Co-Sm system have been shown to be promising as recording media. High coercivities of up to 4.0 kOe have been obtained from Co-Sm films. Recent microstructure characterization of Co-Sm films deposited by the DC magnetron sputtering has shown that the microstructure is composed of the amorphous matrix and crystallites with a grain size of about 5nm . As different sputtering processes have different dynamics for the formation of the nanostructure, phases formed could be different from those predicted by the equilibrium phase diagram. Crystal structure determination is important for understanding the high anisotropy and epitaxy growth of the Co-Sm films. The crystal structure of the crystallites was identified to be a close-packed structure. However, the stacking sequence changes from crystallite to crystallite. This paper describes the detailed high resolution electron microscopy (HREM) study of the stacking sequence of the crystallites in Co-Sm films. It is found that the stacking near the Cr underlayer tends to be hexagonal (ABAB) stacking. As the film grows, the stacking sequence is disturbed and three layer stacking, four layer stacking and random stacking are formed.