Structure and magnetic properties of FePt and FePt/Ag thin films deposited by magnetron sputtering

The magnetic properties and structures of FePt and FePt/Ag thin films deposited by DC and RF magnetron sputtering were studied. The results show that the coercivity of FePt thin films is significantly higher when the stoichiometry is near the equiatomic composition. After annealed at 550 °C for 30 min, FePt and FePt/Ag thin films become magnetically hard with coercivities in the range of 9-10 kOe due to high anisotropy energy associated with the L10 ordered phase. After annealing at the lower temperature of 350 °C for 1 h, FePt films without Ag underlayers were FCC disordered. When Ag underlayers were used, FePt/Ag thin films have a high in-plane coercivity of 6236 Oe. Results indicate that the Ag underlayers are able to reduce the ordering temperature of FePt films. Furthermore, it was found that coercivities of FePt/Ag thin films strongly depend on the sputtering pressure of Ag underlayers. Ag underlayers can slightly reduce the intergranular exchange interactions of the FePt magnetic recording films.