RESONANT X-RAY REFLECTIVITY MEASUREMENTS OF A NI FE ALLOY THIN-FILM -A COMPOSITION PROFILE/

We have measured the composition profile of a Ni/Fe permalloy (0.8 Ni/ 0.2 Fe) thin film using glancing incidence X-ray reflectivity. Resonan t reflectivity measurements were carried out by tuning the X-ray energ y below and above, close and away from the respective K-edges of Fe an d Ni. The information obtained using this method allows a determinatio n of not only the electron density but also the composition profiles o f the Ni/Fe alloy thin film. This non-destructive technique is a promi sing tool for the determination of the chemical composition of thin fi lm. We used a matrix formalism to describe the wave propagation in a c ontinuous medium. In our calculations, we used linear segments to appr oach the local electron density profile at the interfaces and Gaussian factors to account for the rms(root mean squre) roughness due to irre gularities in the boundary position. We were able to obtain excellent fits to the data and get consistent geometry and composition parameter s from the reflectivity measurements at five different X-ray energies. We detected oxidation layers on the top surface and between the alloy thin film and the substrate. We observed also that the Ni/Fe composit ion at the interfaces deviate from that of the bulk of the thin film s ample.