Effects of c-axis correlated pinning in RE123 superconductors

We studied effects of the c-axis correlated disorder on the vortex liquid state in REBa₂Cu₃O₇ (RE123; RE rare earth including Y) superconducting bulk samples. The dip structure for B//c-axis in the angular dependent resistivity appears for all samples used in this study. This means the reduction of the dissipation in the vortex liquid state by the c-axis correlated pinning. We analyzed the reduction of the dissipation by the c-axis correlated pinning by using the resistivity difference between on and off the dip, Δρ^max_n . We found that Δρ^max_n shows the different field dependence for a part of the NEG123 bulk samples in comparison with those of the Y123 bulk samples. The different field dependence of Δρ^max _nis originated from the different type of the c-axis correlated defects such as twin boundary and probably nanolamella.