Electron localization in Co/Ni superlattices

The residual resistivity in Co/Ni superlattices is shown to oscillate as a function of superlattice period for fixed Co to Ni thickness ratio. Additional experimental evidence shows that this behavior is enhanced when randomness is artificially introduced in the individual layer thickness. We analyze this in terms of a scattering mechanism associated with the presence of localized electron eigenstates near the Fermi level in the metallic superlattices. A one-dimensional tight-binding calculation shows that localized states appear close to superlattice periods for which the resistivity exhibits maxima.