Improving the ratio of the grain-boundary and bulk critical currents in YBa_(2)Cu_(3)O_(7-δ) film

摘要

Magneto-optical images of flux patterns in a ring of epitaxial YBa_(2)Cu_(3)O_(7-δ) film with an artificial 10° grain boundary are used to determine the ratio of the grain-boundary critical current to the bulk critical current. This ratio which first increases slowly with temperature is found to make a sharp upturn above 77 K showing that the grain-boundary critical current quickly converges to the bulk value at higher temperatures. From the measured ratio and the grain-boundary critical current obtained from magnetization, the temperature dependence of the bulk critical current is recovered.