Effect of Annealing Process on Residual Strain/Stress Behaviors in FePt Thin Films

We have characterized the dependence of residual strain/stress on annealing process (post- and in-situ annealing) in single-layer FePt films prepared by sputtering onto amorphous glass substrates. A remarkable difference of evolutions in residual strains between post-andin-situ annealed samples was observed by Sin² ψ method using synchrotron radiation. The onset of ordering temperature for both series samples is almost identical (~ 350 °C), verified by x-ray diffraction. Crystalline domain size, measured by x-ray peak breadths, of FePt films indicates a difference between these two series samples, which is associated with evolution of residual strain. We believe that the dynamic stress relaxation is the major factor in discrepancy of the residual stress behavior, since the atomic mobility of adatoms during film deposition for in-situ annealing samples are much higher than that for post-annealed films. It is further deduced that residual strain mechanisms may influence the ordering behaviors and related microstructure of FePt films.