Layered structure analysis of GMR multilayers by X-ray reflectometry using the anomalous dispersion effect

As a basic layered structure for giant magnetoresistive (GMR) heads, NiFe/Cu/NiFe/Ta/Si substrate was measured by X-ray reflectometry at Cu K alpha, Cu K beta and Cu K-absorption-edge energies. The accuracy of both the Cu thickness and the interface width between the upper NiFe and the Cu layers was found to improve in the order Cu K alpha < Cu K beta < Cu K-edge. The final thickness and interface width values obtained from Cu K beta reflectivity are in good agreement with those from the Cu K-edge. The anomalous-dispersion effect is useful in the more accurate analysis of the layered structure of transition metal multilayers because it causes a large difference in the refractive indices of specific elements near the absorption edge. The K beta X-rays, which can be produced from conventional X-ray sources, are also available for the accurate analysis of reflectivity measurements.