Currents In YBa2Cu3O7 Research Articles

Controllable reduction of critical currents in YBa2Cu3O7−δ films

The critical currents in high quality thin films of the high Tc superconductor, YBa2Cu3O7−δ, can be controllably reduced by orders of magnitude using ion irradiation. This reduction in critical current occurs without substantial decrease in Tc or increase in room-temperature resistivity. Using this technique, we have fabricated weak links that exhibit an ac Josephson effect at 77 K.

Orientation dependence of grain-boundary critical currents in YBa2Cu3O7- delta bicrystals.

The critical current densities across grain boundaries have been measured as a function of misorientation angle in the basal plane of bicrystals of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$. For small misorientation angles, the ratio of the grain-boundary critical current density to the bulk critical current density is roughly proportional to the inverse of the misorientation angle; for large angles, this ratio saturates to a value of about $\frac{1}{50}$. These results imply that achieving a high degree of texture both normal to and within the basal plane is important for the obtaining of very high critical currents in pure polycrystalline samples.

Texture formation and enhanced critical currents in YBa2Cu3O7

We report an increase of a factor up to 5 in JC on mixing varying amounts of Ag2O with YBa2Cu3O7. The increase correlates with an increase in texture as seen by x-ray diffraction intensities. Microstructure indicates the formation of platelets with c axis normal to the platelets.

Critical current measurements in YBa2Cu3O7−δ/Sr,Fe samples

The critical currents in YBa2Cu3O7−δ and Sr- (for Ba) and Fe- (for Cu) substituted samples were measured by 4-probe resistive measurements and magnetization experiments. The critical current density Jc, is related..to the underlying microstructure, which differs for all three systems. The field dependence of Jc, and the comparison of the V–I curves measured in the conventional and force-free configuration gives an indication on the effects which determine the critical currents in the superconducting state of sintered bulk samples.