Improved flux pinning in Y_xHo_1-xBa₂Cu₃O_y fabricated by powder melting process

Flux pinning and the peak effect of Y_xHo_1-xBa₂Cu₃O_y melt-textured samples fabricated by a powder-melting-process method are investigated by a SQUID magnetometer in a magnetic field parallel to the c-axis of the samples. It has been found that the partial substitution of Ho for Y can lead to a strong enhancement of flux pinning over a wide temperature and field range in melt-textured YBa₂Cu₃O_y samples. A J_c value as high as 1.3 × 10⁵ A cm^-2 at 77 K and in self-field has been achieved in the Y_0.4Ho_0.6Ba₂Cu₃O_y sample. The enhancement of flux pinning may be attributed to the reduction of Y₂BaCuO₅ particles, the higher density of stacking faults and the paramagnetic moment of Ho³⁺. Contrary to the pure YBa₂Cu₃O_y sample, a peak effect can be observed below 77 K in H ∥ c in the Ho-added superconductors.