Local Structure And Superconductivity In (Bi1.6pb0.4sr2ca2cu3o10+6)1-X(Fe3o4)X Compounds

In this work, a close correlation between variations of critical temperature (Tc) and the hole concentration of (Bi1.6Pb0.4Sr2Ca2Cu3O10+6)1-x(Fe3O4)x systems was studied. The (Bi1.6Pb0.4Sr2Ca2Cu3O10+6)1-x(Fe3O4)x samples were fabricated using the solid-state reaction method, where x ranged from 0 to 0.2. The Tc values of the samples deduced from magnetization versus temperature measurement gradually decreased with increasing the Fe3O4 content (x). To investigate a possible reason for the observed decrease in the values of Tc in the samples, the valence state of copper (V) and the hole concentration (p) in all samples were examined by analyzing the Cu Kedge and Cu L2,3-edge X-ray absorption near edge structure (XANES) spectra. The values of V and p monotonously decreased with the increase in Fe3O4 doping content (x) and agreed with the behavior of Tc. The existence of Fe3+ was confirmed by analyzing Fe L2,3-edge XANES. Hence, Fe3+ ions possibly entered the lattice structure of the samples and filled the holes in CuO2 planes. The degradation of superconductivity in Fe3O4 doped samples was then explained.