Close relation between Mg–Mg bonds and Tc of SiC buffered-MgB2 tapes

Abstract

A series of superconducting tapes were prepared by growing MgB2 film on Hastelloy tapes buffered with SiC buffer layers. When the SiC buffer layer increases in thickness, the superconducting transition temperature (Tc) of MgB2 tapes show slight increment with no depression detected. This Tc behavior may have been originated from the changes occurred in the local structure of MgB2. From EXAFS analysis, the ordering of the Mg–Mg bonds was systematically increased when the thicknesses of SiC buffer layers were decreased. We also found that unlike the relatively random bond lengths of Mg–B bond, the Mg–Mg bond lengths are expanding when SiC adds its thickness, inferring the clear effect of SiC to the Mg–Mg bond lengths. On the basis of the results shown in this letter we argue that SiC buffer layers have significant effects on the local structure of MgB2 which contributes to the fundamentals of superconducting properties of MgB2 tapes.