Effect of the underlayer (Ag, Ti or Bi) on the magnetic properties of Fe/Pt multilayer films

Fe/Pt multilayer films with an Ag, Ti or Bi underlayer were prepared by magnetron sputtering and effect of the underlayer on the magnetic properties of annealed Fe/Pt multilayer films was also investigated. Our results demonstrate that Ag underlayer has little effect on the in-plane coercivity Hc of the Fe/Pt multilayer film due to the formation of Ag and L10-FePt phases in the films. The Hc of Ti/[Fe/Pt]13 film keeps on rising with the increasing annealing temperature Ta up to 500 °C and then decreases with the further increasing Ta. The reason should be attributed to the formation of some intermetallic compounds between Ti and Fe; Pt at a high Ta which is harmful to the structure of L10-FePt. The Hc of [Fe/Pt]13 films is enhanced by the Bi underlayer, which can be understood by considering the promotion of the L10-FePt phase by Bi diffusion.