The origin of (001) texture evolution in FePt thin films on amorphous substrates

A theoretical study has been performed to rationalize the strong evolution of (001) texture during postannealing of deposited Fe50Pt50 thin films on amorphous substrates, by comparing calculated strain energies of several crystals with different orientations under presumed strain conditions. An atomistic calculation method based on an empirical interatomic potential (MEAM) was used to calculate strain and surface energies and atomic force microscope experiments were carried out to confirm the surface energy calculation. The (001) texture evolution could not be explained using traditional factors, the surface energy anisotropy and the in-plane strain. It was found that the strain from the L1(0) ordering transformation that occurs during postannealing can make the (001) crystal (crystal with [001] crystallographic orientation into the surface normal) energetically most stable among those with various orientations. It is proposed that the occurrence of anisotropic strain due to ordering transformations should be considered as a key factor that affects the texture evolution and that enhanced ordering and recrystallization kinetics is necessary to maximize the strain effect.