Evolution of microstructure and residual stress on L10 ordering in FePt thin films with different initial stress states

• Microstructure-stress connection in FePt films was studied.
• Initial stress alters microstructure and stress evolution during annealing.
• Densification induces tensile stress of ~1 GPa before extensive L10 ordering.
• Induced tensile stress can efficiently facilitate the nucleation of L10 phase.
• Compressively initial stress results in a higher ordering temperature .

We have characterized the dependence of microstructure, and internal strain/stress on L10 ordering in 40 nm thick FePt films with different initial stresses. The microstructural and crystallographic results indicate that defect annihilation and grain growth induced an increase in tensile stress of ~1 GPa before extensive L10 ordering. The induced tensile stress can efficiently facilitate the nucleation of L10 phase owing to that the volume expansion of L10 ordering and atomic rearrangement neutralizes the tensile stress. If the as-deposited FePt film has a highly compressive state, the induced tensile stress will be canceled out and ordering is retarded, which results in a higher ordering temperature.