Mossbauer study of impurity effects in Bi-Sr-Ca-Cu-O superconductors in the normal state

Mossbauer spectra of Bi2Sr2Ca1 (Cu1-xFex)2O8+y for iron concentrations up to 5% can be fitted with two doublets. These doublets are assigned to two different environments for the substituting ion in the n = 2 phase. One of them is identified as just a single Fe ion replacing a Cu ion in the Cu-O plane, and the other as clumps of atoms enclosing two or more nearest Fe ions. The existence of this last configuration, which is concentration dependent, is associated with adverse effects upon the conductive properties of these materials. In this paper a third doublet, reported by other authors, is identified as coming from the n=1 phase