The effect of Ag and Cu underlayer on the L1 0 ordering FePt thin films

Abstract

The magnetic properties and structure of FePt, FePt/Ag and FePt/Cu thin films have been studied. After annealed at 350 °C for 1 h, the FePt and FePt/Cu films are FCC disordered, and FePt/Ag thin film has a high in-plane coercivity (6236 Oe). It is indicated that Ag underlayer is able to reduce the ordering temperature of FePt films. 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 L1 0 ordered phase, whereas the in-plane and perpendicular coercivities of FePt/Cu are only about 2831 and 3565 Oe, respectively. It is implied that Cu underlayer is not advantageous in reducing the ordering temperature of FePt films. Note that the coercivity of FePt/Ag films hardly change with increasing Ag underlayer thickness, whereas the FePt/Cu film shows the maximum in-plane coercivity (2831 Oe) at the Cu underlayer of 20 nm, and behaves the soft magnetic properties when the thickness of Cu underlayer is lager than 50 nm at annealing temperature of 550 °C.