Flux pinning by collective stacking faults in Y_0.6Ho_0.4Ba₂Cu₃O_y prepared by powder melting process

The correlation between microstructure and flux pinning of Y_0.6Ho_0.4Ba₂Cu₃O_y (123) sample prepared by the powder melting process method has been investigated. Transmission electron microscopy observations show that there exists a large number of novel stacking faults (double CuO chains) in this sample. The shape of the stacking faults looks like collective stairs. The stacking faults are different from those observed in the conventional melt textured 123 materials and not related to 123/Y₂BaCuO₅ interface. The sample is resintered at 900 °C purposefully in order to reduce the density of stacking faults. The magnetization measurements indicate that the critical current density and irreversibility lines in both field orientations (H∥c and H⊥c) are significantly reduced by the decrease in the density of stacking faults. This means that the collective stacking faults work as effective pinning centers in the 123 superconductors prepared by the powder melting process method in a wide range of temperatures and fields.