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

We have fabricated Y2BaCuO5 (211)-deficient YBCO superconductors through the powder melting process (PMP) and investigated its magnetization curves and magnetic relaxation at different temperatures. It is found that Jc and flux pinning potential are reduced due to a decrease in the 211 content. The Jc value drops with the magnetic field following a power law, Jc ∝ 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. (orig.)