Magnetic order and superconductivity in Bi2Sr2Ca1-xYxCu2O8

Magnetization and probe57 Mossbauer studies of Bi2Sr2Ca1-xYxCu2O8 (x=0"1) at temperatures 4.2"420 K have been performed. For all x values, iron (2% of the Cu) occupies several inequivalent sites. For x=1 the majority of the iron ions respond to the Cu magnetic order and display magnetic order below TN=385 K. At 4.2 K all iron ions display magnetic hyperfine structure. For x=0.8 and 0.6, TN decreases to 290(15) and 150(20) K, respectively. For x=0, in the superconducting state, none of the iron is ordered magnetically even at 4.2 K; however, a majority of the iron ions display Mossbauer spectra with paramagnetic hyperfine structure typical of long spin-relaxation times. The magnetization and Mossbauer studies yield a full superconductivity-antiferromagnetism phase diagram with a critical value of xc=0.5.