Enhancement of post-annealing stability in Co/Ni multilayers with perpendicular magnetic anisotropy by Au insertion layers

Abstract: Enhancement of post-annealing stability in Co/Ni multilayers with perpendicular magnetic anisotropy (PMA) was obtained by inserting Au layers into Ni/Co interfaces. After annealing at 350 °C, the effective magnetic anisotropy density (K_eff) for Ta(3)/Pt(2)/[Co(0.3)/Ni(0.6)/Au(0.3)] × ₃/Co(0.3)/Pt(1)/Ta(3) (in nm) keeps at 0.48 × 10⁵ J·m⁻³. Scanning transmission electron microscopy-high-angle annular dark field (STEM-HAADF) analysis shows that the diffusion between Ni and Co layers is obstructed by the Au insertion layers among them, which is responsible for the post-annealing stability enhancement of the multilayers. Multilayers with Pt insertion layers were also investigated as reference samples in this work. Compared with Pt-layer-inserted Co/Ni multilayers, the Au insertion layers are found to bring seldom interfacial PMA to the multilayers, making it competitive in being employed to enhance the post-annealing stability of PMA Co/Ni multilayers which are used for magnetic random access memory devices (MRAM).