INTERFACIAL STRUCTURE AND GIANT MAGNETORESISTANCE IN FE CR SUPERLATTICES/

A correlation between interfacial structure and giant magnetoresistanc e (GMR) has been established for Fe/Cr superlattices [1-8]. However, p revious studies were qualitative in that the interfacial structural di sorder was expressed in terms of growth temperature, sputtering pressu re or annealing temperature. In order to understand more quantitativel y 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 successivel y higher temperatures, both samples having initial GMR > 50 %. Such an neals are known to increase the thickness of the Fe/Cr interface throu gh atomic diffusion, a structural change which can be characterized qu antitatively by XRD. The advantages of high intensity and anomalous di spersion provided by synchrotron radiation has greatly contributed to the quality of our x-ray data, for which the use of simulation program s has allowed a robust and precise extraction of several structural pa rameters for the two samples, including the Fe/Cr interfacial thicknes ses.