Magnetic properties and microstructure of the granular films processed by annealing Fe-Pt based multilayers

In this paper, Fe/FePt or Fe₃Pt/FePt exchange coupled thin films are fabricated by annealing Fe/Pt, Fe/FePt and Fe₃Pt/FePt multilayers. The multilayer thin films, 52.8 nm thick, are fabricated by dc magnetron sputtering. Annealing of the samples at 450°C, 700°C, and 800°C is done for 1 h after the deposition. The microstructures are characterized by XRD and TEM. With annealing temperature of 450°C, the film fabricated from the FePt/Fe₃Pt film shows higher coercivity H_c(8 kOe) than that of Fe/Pt and Fe/FePt. This is the same for the films annealed at 700°C in which FePt/Fe₃Pt film has H_c=12 kOe. The H_c increase is due to the progress of the ordering. The FePt/Fe₃Pt film has larger H_c compared to Fe/FePt because of its rich Pt composition.