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Fe40Co60 epitaxial thin films are prepared on L10 ordered Fe60Pt40 underlayer by ultrahigh vacuum multiple dc-sputtering systems. Magnetic properties of the Fe60Pt40 (10 nm)/Fe40Co60 (t nm) bilayer films are investigated. When the FeCo thickness is less than 3 nm, the easy magnetization axis of FePt/FeCo bilayer film is perpendicular to the film plane. Compared with FePt/Fe and FePt/Co films, FePt/FeCo bilayer films possess not only higher anisotropy field Hk but also larger magnetic anisotropy energy Ku, which may be due to the perpendicular magnetic anisotropy yielded by the tetragonal distorted FeCo layer on FePt, while the magnetic easy axes of Fe and Co layers lie in the film plane. Meanwhile, saturation magnetization of FePt/FeCo film increases reasonably because of the high Ms value of FeCo component. These results indicate that the FePt/FeCo bilayer films which possess both large magnetic anisotropy energy Ku and high saturation magnetization Ms have great potential for using as the magnetic recording media, and also give a clue to develop a new type of permanent magnet without rare-earth metals.

Tetragonal distorted Fe 1Àx Co x (0 x 1) thin films are prepared on L1 0 ordered Fe 0.6 Pt 0.4 underlayer. The dependences of FeCo alloy composition on magnetic anisotropy energy (MAE) are investigated. Based on the LLG simulation, the tetragonal distorted Fe 1Àx Co x films show maximum positive magnetic anisotropy energy when the Co composition is around 60 at. %, while the MAE decreases and shifts to negative when the composition is close to pure Fe or Co. The experiment results prove that the MAE can be tuned by varying the alloy composition. Furthermore, the magnetic moments of Fe and Co in distorted Fe 0.4 Co 0.6 films are studied by the X-ray magnetic circular dichroism spectroscopy. The enhanced orbit moments which come from the lattice distortion increase the magnetic anisotropy energy of Fe 0.4 Co 0.6 film. V C 2015 AIP Publishing LLC.