We have successfully grown BSCCO single crystals showing high critical current density of 2×106 A/cm2 at 20 K. Magneto-optical observation showed that the sample exhibited inhomogeneous penetration of magnetic flux correlated with the crystal b-axis. According to compositional analyses using wave-dispersive spectrometry (WDS), the crystals consisted of two phases, for which the Ca content was slightly different. It was also found that the values of the overall critical current density derived from the magnetization measurements depend on the portion of these two regions. Transmission electron microscopy revealed that strong pinning materials contain the region with a short incommensulate modulation period compared to the previously reported values, which might be responsible for extremely high J c values.
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