Interlayer Thickness Effects on Magnetic Properties of X/FePtAg (X = FePt/Fe and Fe/FePt) Trilayers

A soft/hard FePt/Fe/FePtAg and Fe/FePt/FePtAg trilayers with perpendicular magnetization were prepared on a glass substrate. Inserting disordered FePt layer allowed modification of magnetic anisotropy of the Fe/FePtAg sharp interface to Fe/FePt/FePtAg stepwise interface. The out-of-plane coercivity field was modulated as a function of the FePt thickness because of the interface coupling attenuation between Fe and FePtAg. The coercivity was inversely proportional to the FePt thickness as evidenced by the pinning effect at the stepwise interface. Additionally, the out-of-plane magnetization was controlled by domain wall pinning effect. The in-plane magnetization reversal processes occurred in two steps like in exchange spring systems and attributed to the domain wall nucleation and its propagation from Fe/FePt layer into FePtAg layer.