Vortex pinning phase diagram for various kinds of c-axis correlated disorders in RE123 films

The critical current density J_c and resistivity ρ of REBa₂Cu₃O_x (RE123) films were evaluated in high magnetic field and wide temperature regions. We use three different samples such as a heavy ion irradiated Y123 film, a BaZrO₃ (BZO) added Y123 film and a low temperature growth Sm_1-xBa_2+xCu ₃O_y (LTG-Sm123) film. In these films, there exist the different c-axis correlated disorders like columnar shaped fission tracks for the heavy ion irradiated Y123 film, columnar shaped BZO precipitates for the BZO added Y123 film and edge dislocations at grain boundaries for the LTG-Sm123 films. The large peak of the angular dependence of J_c for B//c direction was observed for all samples measured in this study in a low field region, suggesting that the c-axis correlated pinning works well for these samples. However, we found that the behavior of the J_c peak for B//c strongly depends on a sort of c-axis correlated pinning centers. In the case of the columnar shaped fission tracks in the Y123 film, the J_c peak for B//c increases monotonically with increasing a magnetic field and seems to be connected with the dip structure in the angular dependence of ρ. In the case of the columnar shaped BZO precipitates, however, the J_c peak for B//c vanishes in a high field region above a few tesla and no dip behavior of ρ was observed. On the contrary, in the case of the edge dislocations for LTG-Sm123 film, the J_c peak for B//c shrinks with increasing field and almost vanishes. But it grows again with further increasing a magnetic field and the dip of the angular dependence of ρ is also observed. Hence the vortex pinning phase diagram strongly depends on a sort of c-axis correlated pinning centers. It is considered that these different behaviors of the J _c peak for B//c are related to the competition of the random and c-axis correlated pinnings.