Magnetic Properties of Exchange-Coupled L10-FePt/Fe Composite Elements

Exchange-coupled LI0-FePt/Fe composite systems with out-of-plane anisotropy are produced to study the influence of the soft magnetic layer thickness and of the character of the interface between hard magnetic L1(0)-FePt and soft magnetic Fe on the magnetic properties. By the soft magnetic layer thickness d(Fe) the coercivity can be tailored according to a 1d(Fe)(2) relation. By depositing part of the Fe Fe layer at elevated temperatures a graded interface between the L1(0)-FePt layer and the Fe layer is formed which allows an additional fine tuning of the coercivity. This behavior is confirmed by micromagnetic numerical simulations. The simulations furthermore show that the reversal behavior and the thermal stability are nearly the same for out-of-plane and in-plane anisotropy of L1(0)-FePt. If the remanent magnetization configuration shows deviations from the homogeneous magnetization distribution an alternative low-field thermal reversal mode occurs.