CRITICAL-CURRENT DENSITY IN EPITAXIAL YBA2CU3OX FILM

The critical current density J(c) of YBa2Cu3Ox epitaxial film as a fun ction of the angle theta between magnetic field and ab-plane with H pe rpendicular to I and temperature was measured in various magnetic fiel ds. Maxima of J(c) were observed near 0 degrees and 90 degrees, respec tively, with that for the latter higher than that for the former. A de viation of J(c)(0 degrees) peaks from 0 degrees and the asymmetry of J (c)(theta) with respect to theta = 90 degrees are observed in the fiel d below 0.5 T. It is found for the first time that n is a function of magnetic field in the relation J(c) alpha(1-t)(n).