抄録
Critical current characteristics of a bulk YBaCuO superconductor prepared by Quench and Melt Growth (QMG) process were investigated as a function of magnitude and direction of magnetic field and temperature. The QMG processed samples have highly oriented microstructure and are also free from grain boundaries which are considered to act as weak links. Magnetization curves were measured using a vibrating sample magnetometer. Critical current density (Jc) was estimated using the Bean type critical state model. When the magnetic field was applied along c-axis, the Jc perpendicular to c-axis was 1.5×104A/cm2 at 77K and 1T, while the Jc was 5×105A/cm2 at 4.2K and 4T in the same condition. The Jc exponentially increased with decreasing temperature. Resistive measurements were also done by using a four probe method at 77K. Large anisotropy of the Jc was observed with the direction of the applied field. It was found that Jc decreased with the field much more rapidly when the field was applied along c-axis and this was attributed to the small Bc2 (about 8T) in this direction.
