Bismuth layer properties in the ultrathin Bi–FeNi multilayer films probed by spectroscopic ellipsometry

Using wideband (0.5–6.5 eV) spectroscopic ellipsometry, we study ultrathin [Bi(0.6–2.5 nm)–FeNi(0.8,1.2 nm)]N multilayer films grown by rf sputtering deposition, where the FeNi layer has a nanoisland structure and its morphology magnetic properties change with decreasing nominal thickness. From model simulations of ellipsometric angles, Ψ(ω) Δ(ω), complex (pseudo)dielectric function spectra Bi were extracted. The obtained results demonstrate that can possess surface metallic conductivity, which is strongly affected in GMR-type Bi–FeNi structures.