Interface structure in magnetic multilayers using x-ray standing waves

Abstract

It is demonstrated that interface structure in thin film nanostructures can be studied with a depth resolution of a fraction of a nanometer by using x-ray standing waves generated by a multilayer mirror used as a substrate. Two interfaces of a few nm thick Fe layer in magnetic trilayer structures $\mathrm{Tb}∕\mathrm{Fe}∕\mathrm{Tb}$ and $\mathrm{Cr}∕\mathrm{Fe}∕\mathrm{Cr}$ could be clearly resolved using x-ray standing waves generated by an underlying $\mathrm{W}∕\mathrm{Si}$ multilayer mirror. It is found that in both the cases rms roughness of the two interfaces Fe-on$\text{\ensuremath{-}}\mathrm{Tb}(\mathrm{Cr})$ and $\mathrm{Tb}(\mathrm{Cr})$-on-Fe are not equal. For example, roughness of $\mathrm{Fe}\text{\ensuremath{-}}\mathrm{on}\text{\ensuremath{-}}\mathrm{Tb}$ interface is $1.2\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, while that of $\mathrm{Tb}\text{\ensuremath{-}}\mathrm{on}\text{\ensuremath{-}}\mathrm{Fe}$ interface is $0.7\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. The technique is particularly suitable in systems in which x-ray scattering contrast between adjacent layers is poor.