Influence of Co layer thickness on the structural and magnetic properties of (Pt/CotCo)3/PttPt/IrMn multilayers

The correlated effects of the insertion of a Pt spacer between ferromagnetic and antiferromagnetic layers and of the variation of the Co layers' thickness on the structural and magnetic properties of [(Pt/Co-tCo)(3)/Pt-tPt/IrMn](n) multilayers have been studied. Samples with n = 1 and 7, t(Co) = 0.4 and 0.6 nm, t(Pt) = 0 and 0.4 nm have been investigated by tomographic atom probe and superconducting quantum interference device magnetometry. For spacer-free samples (t(Pt) = 0), the structural investigation shows that when t(Co) = 0.4 nm, Mn and Ir atoms diffuse deeply into the (Pt/Co)(3) multilayers. In contrast for t(Co) = 0.6 nm, the Mn and Ir diffusion is much reduced. Because Pt acts as a barrier against the Mn and Ir diffusion, this difference is less pronounced in samples with Pt insertion. The hysteresis loops shapes, the exchange bias fields and the saturation magnetization values were correlated with the structural properties of these samples and discussed, taking into account the susceptibility, exchange stiffness and perpendicular magnetic anisotropy.