Null-ellipsometry investigations of the optical properties and diffusion processes in spin-valve structures based on Co and Cu

The influence of annealing temperature (T_a = 300-900 K) on optical properties of the Au (4 nm)/Co (3 nm)/Cu (6-12 nm)/Co (20 nm)/SiO₂/Si spin-valve structures was studied. The model of Co, Au, and Cu atom interdiffusion was proposed based on the experimental data analysis. The formation of solid solutions at the thin layer interfaces Au/Co and Cu/Co was studied, and as a result the most intensive formation of solid solutions was identified at annealing temperature of T_a = 750 K. The optical parameters of the samples were calculated using the genetic algorithm. The spin-valve systems remain relatively unperturbed until 750 K, but the optical properties change significantly from 750 to 900 K. It can be explained by the formation of the interphase in multilayer thin film systems.