Ferromagnetic resonance and spin-wave exchange stiffness of FeGaB/Al2O3 multilayer thin film stack for microwave applications

Abstract

In this article, we have illustrated the deposition of multilayer film stack of Ta (5 nm)/[FeGaB (15 nm)/Al2O3 (3 nm)] n/Ta (3 nm)/Al2O3 (2 nm); n = 1,5, and 10, onto Si substrates, and studied magnetodynamic properties with multilayer thickness and temperature dependence. The results of surface morphology of thin film stacks suggest dipolar coupling generates for n = 5 and 10 thin film stack, which influence the ferromagnetic absorption results. From results of ferromagnetic resonance spectroscopy (FMR), the resonance peak for each excitation frequency provides the effective magnetization, the gyromagnetic ratio and damping factor. The damping factor for multilayer stack n = 1 shows a lower value compared to the other two samples. The multilayer stack provides perpendicular surface magnetic anisotropy (ks) from thickness dependence of effective magnetization. The analysis of spin-wave resonance spectra at multiple frequencies allows manipulate the exchange stiffness (D) of multilayer film stack n = 5 and n = 10 and temperature dependence the exchange stiffness follows the itinerant-electron model (T2 law) and suggests electron - magnon scattering exists in the thin film stack.