Structure and Magnetic Properties of Doped Co and Fe-Bi sub 2 Sr sub 2 Cu sub (1-x) M sub x O sub y Phases.

The structure and magnetic properties of the Bi sub 2 Sr sub 2 Cu sub (1-x) M sub x O sub y (M = Co and Fe) materials were studied. The limits of solid solution formation are at x=0. 5 for the Fe system and x=1 for the Co system. Crystals of the new Bi sub 2 Sr sub 2 CoO sub y phases were grown and the structure established by x-ray crystallography. The subcell is the same as that of the 10K superconductor, Bi sub 2 Sr sub 2 CuO sub y, but the superstructure is different, as it exhibits a commensurate modulation of periodicity 4 instead of 5. Extra oxygen is accommodated in the Bi layers, as in Bi sub 2 Sr sub 3 Fe sub 2 O sub y, and the structure of the Bi-O layers can be described as 50% rocksalt-type and 50% oxygen- deficient perovskite for x=1, but with disorder at the oxygen positions.