Microstructure evolution, magnetic and mechanical properties of FePt/B 4C multifunctional multilayer composite films

FePt/B₄C multilayer composite films with a Fe/Pt two-layer structure and a Fe/Pt/Fe sandwich structure were prepared by magnetron sputtering and subsequent annealing in vacuum. When the B₄C interlayer thickness of the FePt/B₄C films is bigger than 3 nm, a stable value of grain size, coercivity and hardness is observed. The characterizations of the microstructure demonstrate that the diffusion of B and C atoms in the FePt layer is so finite that the multilayer structure of the FePt/B₄C films is maintained after annealing at 500 °C for 30 min. The finite diffusion of B and C atoms is responsible for the FePt grain growth confinement, grain and layer separation and eventually induces the stable value mentioned above. The single composite films may find application in substituting the traditional three-layer structure commonly used in the present data storage technology. © 2007 IOP Publishing Ltd.