Influence of the annealing atmosphere on the structural properties of FePt thin films

FePt thin films with a thickness of 30 nm were deposited by dc magnetron sputtering at room temperature onto SiO₂(100 nm)/Si(100) substrates. These films were post-annealed in a temperature range of 500 °C to 900 °C for 30 s in three different atmospheres - N₂, Ar, and forming gas (Ar+H₂ (3 vol. %)). Irrespective of the annealing atmosphere, the chemically ordered L1₀ FePt phase has formed after annealing at 500 °C. Higher annealing temperatures in N₂ or Ar atmosphere resulted in a strong increase in grain size and surface roughness but also in the appearance of a pronounced (001) texture in the FePt films. However, these films show the presence of iron oxide. In contrast, annealing in forming gas atmosphere suppressed the oxidation process and resulted in a reduced grain size and lower surface roughness. However, no (001) - but a strong (111) - texture was obtained after annealing at 700 °C, which might be related to the reduced unit cell tetragonality and incorporation of hydrogen to the FePt lattice. Thus, this study clearly demonstrates that the oxygen/hydrogen content plays an important role in controlling the crystallographic orientation during post-annealing.