Layered synthetic microstructures: Importance of a combined X-ray standing wave and X-ray reflectivity analysis

Layered synthetic microstructures consisting of thin layers of alternating elements or compounds have unique structural, electronic and magnetic properties with a wide range of applications. For such multilayer systems it is important to correlate the measured proper-ties with structure and composition so that preparation techniques can be optimized to yield high performance materials. For magnetic multilayers where alternating layers are magnetic and nonmagnetic materials, a small amount (even a few percent) of magnetic impurity (either from the magnetic layers or external) in the nonmagnetic layer can change the magnetic coupling and magnetoresistance significantly. Determination of such small concentrations by X-ray reflectrometry is often very difficult. Layer composition is more accurately determined by X-ray standing wave (XSW) analysis, while interface roughness is more accurately determined by the X-ray reflectivity (XRR) technique. It is shown that for periodic multilayers, a combined XSW and XRR analysis provides more accurate compositional and microstructural information overcoming the deficiencies of the individual techniques.