Interfacial structure and giant magnetoresistance in Fe/Cr superlattices

Abstract
A correlation between interfacial structure and giant magnetoresistance (GMR) has been established for Fe/Cr superlattices [l-8]. However, previous studies were qualitative in that the interfacial structural disorder was expressed in terms of growth temperature, sputtering pressure or annealing temperature. In order to understand more quantitatively the effects of interfacial structure on GMR, we have undertaken [9] parallel measurements of x-ray diffraction (XRD) and magnetoresistance for two Fe/Cr samples subjected to a series of anneals at successively higher temperatures, both samples having initial GMR > 50 %. Such anneals are known to increase the thickness of the Fe/Cr interface through atomic diffusion, a structural change which can be characterized quantitatively by XRD. The advantages of high intensity and anomalous dispersion provided by synchrotron radiation has greatly contributed to the quality of our x-ray data, for which the use of simulation programs has allowed a robust and precise extraction of several structural parameters for the two samples, including the Fe/Cr interfacial thicknesses.