Critical currents in bulk samples of YBa2Cu3O7−δ and DyBa2Cu3O7−δ

✍ Scribed by J. Aponte; H. Abache; M. Octavio

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 363 KB
• Volume: 29
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(89)90182-3

✦ Synopsis

We have performed four probe transport measurements of the critical current in bulk samples of the high-Tc superconductors YBa2Cu307_~ and DyBa2Cu3074. We found that over a range of temperatures the critical current varies linearly with (T c-T). This result indicates that these ceramics behave as a three-dimensional percolating network of Josephson junctions. Very close to the critical temperature, the critical current versus temperature curves are found to have a nonlinear tail which, in some of the samples, is of the form/cOC (T c -T)V with v ~ 3/2. This is the usual dependence of depairing critical currents as predicted from Ginzburg-Landau theory. We have determined the temperature at which / c departs from the linear behaviour and we have compared it to the predictions of Clem et al. Agreement is found if the effective grain diameter is chosen between 0.005 #m and 0.1 /zm. This is much less than the average size of the grains as measured in the microscope. We conclude that intragrain domains between twin boundaries determine the scale of the percolating network of Josephson junctions.