Transport superconducting properties of grain boundaries in Tl1Ba2Ca2Cu3Ox thin films

In order to investigate weak link properties in the Tl1Ba2Ca2Cu3Ox[Tl-(1223)] system, we measured the transport properties of artificially grown grain boundaries in Tl-(1223) films. Epitaxial thin films were grown on SrTiO3 bicrystal substrates with five tilt angles of 5°, 10°, 15°, 24°, and 36.8°. We found that the grain boundaries Jc (Jcg.b.) of large tilt angles (θ≥15°) at 77 and 5 K were substantially less than intragrain Jc(Jcg) and limited by a weak link. However, the Jcg.b./Jcg values for low tilt angle grain boundaries (θ≤10°) were almost unity. Moreover, magnetic-field history dependent Jc values for low tilt angle grain boundaries were not observed in a low magnetic field (<0.1 T). These data indicate that the low tilt angle grain boundaries do not work as a weak link and retain high Jc.