Magnetization and magnetic anisotropy of Co/W multilayers

The magnetic properties of polycrystalline Co/W multilayers have been inves tigated using angular-dependent ferromagnetic resonance (FMR) and SQUID mag netometry. Two sets of samples with a constant thickness of Co layers (CoI: d(Co) = 1 nm and CoII: d(Co) = 2.5 nm) and varying W layer thickness (1 to 7 nm) were studied. The structure of the multilayers was analysed by X-ray reflectivity (XRR) and X-ray diffraction (XRD). We found a well-defined (1 10) texture and coherent structure of the multilayers. The saturation magne tization of Co is smaller than that of bulk Co which is explained by a redu ced Co moment at the interfaces of more than 50%. A narrow FMR linewidth on the order of 200 Oe at 9.5 GHz is observed for CoI and Cell multilayers wi th d(W) approximate to 1 nm that indicates the high magnetic homogeneity of the Co layers. The second and fourth order magnetic anisotropy constants ( K-2 K-4.1) are found to be independent of the Co layer thickness. K-2 is in versely proportional to the W layer thickness, which is due to the changing lateral lattice mismatch with the W layers.