A study of magnetic properties in Y₂BaCuO₅-deficient melt-processed YBCO

We have fabricated Y₂BaCuO₅ (211)-deficierit YBCO superconductors through the powder melting process (PMP) and investigated its magnetization curves and magnetic relaxation at different temperatures. It is found that J_c and flux pinning potential are reduced due to a decrease in the 211 content. The J_c value drops with the magnetic field following a power law, J_c ∝ B^-m, (m < 0.6), which can be interpreted in the framework of the flux creep model and the collective pinning theory. The magnetic relaxation measurement shows that the Anderson-Kim model fits our data quite well in the temperature range 56 to 77 K. The origin of the fishtail effect in the magnetization curve is also discussed.