Here, MgB2 was doped with 57Fe and 57Co in order to probe the electronic structure of the superconductor by Mössbauer spectroscopy. Simultaneous SEM–EDX studies showed that both Fe and Co were incorporated into the host lattice to some extent. Mössbauer spectroscopy indicated that Fe2B and FeB were also formed during preparation. At higher Fe contents, Fe2B appeared as a secondary phase in X-ray diffraction, and CoB was detected at substitution levels of 10mol% or more. Both Fe and Co doping modestly decreased TC(0). The Co and Fe were found to substitute at Mg sites in the lattice. The Mössbauer parameters for 57Co and 57Fe were consistent with a metallic environment.

Local Environments of Iron and Cobalt in Doped MgB2 Superconductors. E.Kuzmann, Z.Homonnay, Z.Klencsár, M.Kühberger, A.Vértes, G.Gritzner: Superconductor Science and Technology, 2002, 15, 1479-85