Abstract
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 Bi 2.1Sr 1.9Ca 1.0(Cu 1-yFe y) 2O x single crystal was y = 0.000, 0.005, 0.016 and 0.022. A strong field and temperature dependence of J c has been observed for the samples with y = 0.022 and 0.016 doping. At zero field, large J c 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 with y = 0.016 and 0.022 had lower values of J c than samples with y = 0.000 and 0.005. Similarly, for H < 500Oe samples with y = 0.000 and 0.005 had lower Jc than the more strongly doped samples. For H > 500Oe, it was the opposite. 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 indicated that the iron in the CuO 2 planes acted as an effective pinning centre. The effectiveness of the pinning centres was strongly influenced by the field and thermal excitations.
Published Version
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