Variable wavelength grazing incidence x-ray reflectivity measurements of structural changes on annealing Cu/NiFe multilayers

Grazing incidence x-ray reflectivity spectra from copper/permalloy multilayers have been recorded as a function of incident x-ray energy under conditions of fixed scattering vector. From the smoothly varying part of the spectrum, it is possible separately to determine the density and composition as the energy is scanned through the K edges of the constituent elements. From the fit to model layer structures, we determine that there exists a strained layer of permalloy at the permalloy/copper interface that relaxes towards the unstrained density of permalloy on annealing. No such layer exists at the copper/permalloy interface. Cobalt doping results in the formation of a layer of mixed CoNiFe composition, rather than a single Co layer. Oscillations in the spectra above the absorption edges are analyzed in a similar manner to that for diffraction anomalous fine structure and enable the short range order within the layers to be determined. No changes are observed in the Cu or Co environments, but a reduction in the in-plane first shell distance around the Ni atoms is found on annealing.