Field and temperature dependence of critical current density of Fe doped Bi2212 single crystals

Critical current density Jc as a function of magnetic field and temperature has been studied in Fe-doped and pure Bi2212 single crystals. The nominal iron content in the Bi2.1Sr1.9Ca1.0(Cu1-yFey)(2)O-x single crystal was y = 0.000, 0.005, 0.016 and 0.022. A strong held and temperature dependence of Je has been observed for the samples with y = 0.022 and 0.016 doping. At ze ro field, large Je was observed for these samples up to 40K, as compared to the samples with y = 0.005 and y = 0.000. However, for T > 40K, samples wi th y = 0.016 and 0.022 had lower values of J(c) than samples with y = 0.000 and 0.005. Similarly, for H < 5000e samples with y = 0.000 and 0.005 had l ower Jc than the more strongly doped samples. For H > 5000e, it was the opp osite. The samples with y = 0.005 were found to show large Jc over a wider range of temperatures and fields than any other samples studied This indica ted that the iron in the CuO2 planes acted as an effective pinning centre. The effectiveness of the pinning centres was strongly influenced by the fie ld and thermal excitations.