Current transport across grain boundaries in TlBa2Ca2Cu3O(x) thick polycrystalline films and YB2Cu3O7 step edges

摘要

We have performed transport measurements in magnetic fields (H//c) up to 10T on a series of YBa(sub 2)Cu(sub 3)O(sub 7) grain boundaries induced by epitaxial growth on a substrate containing a series of step edges. For this material we find an activation energy which goes as U(T)(approximately)(1-t). Electric field versus current density curves taken at a constant temperature while varying the magnetic field allows a determination of the magnetic field dependence of the activation energy using the Ambagaokar-Halperin Model. These values agree with results extracted from the resistive transitions. Similar characterizations of a sample of TlBa(sub 2)Ca(sub 2)Cu(sub 3)O(sub x) are also presented. The temperature dependence of the activation energy for this system may be summarized as U(T)(approximately)(1-t)(sup 2), suggesting that the grain boundaries behave as SNS juctions.