Investigation of structural and magnetic properties of multilayered ferromagnetic cobalt films

In this thesis study, the aim was to control the critical parameters determining the performance of ferromagnetic materials used as information carriers in spintronic memories and circuits through different interfaces. In this context, the structural, static, and dynamic magnetic properties of Cobalt-based thin films produced with capping layers having different spin-orbit coupling characteristics (Cu, CuIr, and Pt) were investigated using X-ray Diffraction, Vibrating Sample Magnetometry, and Ferromagnetic Resonance techniques, respectively. XRD analyses revealed that the crystal quality improved with increasing Co film thickness, and the structure evolved from a strained face-centered cubic (fcc) phase to a hexagonal close-packed (hcp) phase exhibiting bulk-like properties. While static magnetic measurements confirmed that the saturation magnetization of the films was consistent with the literature, no magnetic dead layer was observed in the Co/Cu system; however, a magnetic dead layer of approximately 0.21 nm thickness, resulting from atomic intermixing, was detected at the Co/CuIr interface. Dynamic analyses performed using the FMR technique determined that magnetic damping was controlled by Gilbert damping and Two-Magnon Scattering mechanisms. The linear increase of the Gilbert damping parameter with inverse Co thickness experimentally demonstrated the existence of the spin-pumping mechanism in the systems. In the comparison of the thin films, it was observed that the Pt capping layer, with its strong spin-orbit coupling, exhibited ideal spin-sink behavior, providing the highest damping and anisotropy values. The CuIr alloy showed an intermediate damping performance due to impurity scattering, while the Cu layer, with weak spin-orbit coupling, created the weakest effect in damping the spin current. This study demonstrates that magnetic properties can be precisely modified through interface material selection and thickness optimization.