Effect of annealing on the microstructures and the magnetic properties of [Fe/Pt]16 multilayers on MgO (001) substrates

[Fe/Pt](16) multilayers were deposited on MgO (001) single-crystal substrates by magnetic sputtering at various substrate temperatures to explore the effect of annealing on the microstructures and the magnetic properties. Results show that the FePt alloy becomes ordered at about 300 A degrees C and reaches a completely-ordered state at about 400 A degrees C. FePt films deposited at temperature above 300 A degrees C have a (001) preferred texture, which shows that the L1(0) FePt films have perpendicular magnetic anisotropy. The out-of-plane coercivity increases when the sample is transformed from [Fe/Pt](16) multilayers to a L1(0)-FePt alloy and increases by one order of magnitude when the morphology of the L1(0) FePt alloy evolves from a continuous to a granular surface.