Permittivity features of multilayer nanoisland systems [FeNi–Al2O3

Abstract

We study the permittivity (ε) of multilayer nanoisland systems [FeNi–Al2O3]N with different layer thicknesses using spectral ellipsometry. A “metallic” behavior of the permittivity (Re(ε)<0) is found in structures with island FeNi layers, when there is a strong exchange interaction between the layers (dielectric layer thickness d<2 nm). When the exchange interaction in structures is strongly suppressed (Al2O3 layer's thickness d>4 nm), Re(ε)>0, which corresponds to the dielectric behavior of the permittivity. We conclude that the exchange interaction has a significant effect on the permittivity of structures. We also show that the Re(ε) dependences on the FeNi layer thickness for multilayer and single-layer structures are very close when the dielectric layer thickness d>4 nm.