The critical current density flowing across low angle grain boundaries in YBa2Cu3O7−δ thin films has been studied magnetometrically. Films (200 nm thickness) were deposited on SrTiO3 bicrystal substrates containing a single [001] tilt boundary, with angles of 2, 3, 5, and 7 degrees, and the films were patterned into rings. Their magnetic moments were measured in applied magnetic fields up to 30 kOe at temperatures of 5 - 95 K; current densities of rings with or without grain boundaries were obtained from a modified critical state model. For rings containing 5 and 7 degree boundaries, the magnetic response depends strongly on the field history, which arises in large part from self-field effects acting on the grain boundary.
@article{arxiv.cond-mat/0308328,
title = {Self-organized current transport through low angle grain boundaries in YBa$_2$Cu$_3$O$_{7-\delta}$ thin films, studied magnetometrically},
author = {J. R. Thompson and H. J. Kim and C. Cantoni and D. K. Christen and R. Feenstra and D. T. Verebelyi},
journal= {arXiv preprint arXiv:cond-mat/0308328},
year = {2009}
}