X-ray reflectivity of ruthenium nano-oxide layer in a CoFe-Ru-CoFe trilayer system

A grazing incidence X-ray reflectivity technique is used to determine electron density profile(EDP) as a function of depth in CoFe-Ru-CoFe and CoFe-Ru nano oxide layer(NOL)-CoFe trilayers. Four trilayers with ruthenium thicknesses of 8,8.5 and 9 \AA \hspace{.08cm} and one with Ru8.5\hspace{.05cm}\AA\hspace{.05cm}NOL, prepared by a dc planetary sputtering system, were investigated. For all samples, EDP shows a central peak which is related to the Ru layer. Natural oxidation in all samples introduces a graded EDP of the top CoFe layer that decreases gradually to zero. The large surface resistivity of Ru8.5 \AA\hspace{.05cm} NOL compared to Ru 8.5\AA\hspace{.08cm} can be related to the remarkable difference between their EDP.