Effects of Interfacial Layers on Magnetization Dynamics of [Fe75Co20Cu5/Cu(x)]30 Multilayer Nanowires

A series of highly ordered multilayer [FeCoCu/Cu(x)](30) (0 <= x <= 40 nm with FeCoCu layer thickness fixed 1000 +/- 100 nm) nanowire arrays in alumina membrane (200 nm diameter) was fabricated by electrodeposition from a single electrolytic bath. The body-centered cubic (bcc) phase of FeCoCu-alloy separated by a well-defined face-centered cubic (fcc) phase of Cu spacer is confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. The objective of the present investigation is to tune the magnetic properties through inter- and intra-wire interactions between the FeCoCu layers separated by non-magnetic Cu(x) layers in the multilayer nanowire array. Ferromagnetic resonance (FMR) study was performed in a flip-chip geometry to explore the magnetization dynamics. FMR measurements confirm the decrease of resonance field ( Hr), whereas resonance linewidth (Delta H) and FMR absorption increase with the increase in the Cu layer thickness. It may be argued that through inter-/intra-nanowires interactions, the Landau-Lifshitz-Gilbert damping provides the most physically sensible magnetization relaxation in multi-layered nanowires system. The values of the Gilbert damping parameters (intrinsic and extrinsic), obtained from the FMR linewidth analysis, exhibit a decrease from FeCoCu nanowire to [FeCoCu/Cu(5 nm)] nanowire. With further increase in the Cu thickness, both these parameters were observed to have increased.