Angular hysteresis in the critical current of YBa₂Cu₃O₇low-angle grain boundaries

The dependence of the critical current density, J c , on the orientation of an applied magnetic field has been measured for two YBa 2 Cu 3 O 7 [001]-tilt low-angle grain boundaries. As the field is rotated in the boundary plane, a marked hysteresis in the variation of J c with angle is observed. The effect is visible as a clear shift in the position of the intrinsic pinning peak as a function of the direction of field rotation (θ + or θ - ). In addition, we observe a switch over from J c (θ + ) to J c (θ - ) in just a few degrees of field rotation and find angular hysteresis to be increasingly pronounced at both low field and low temperature. Similar measurements taken on intragranular tracks displayed no hysteresis, suggesting the effect is associated with the presence of the grain boundary. We explore one possible model, involving flux trapping within the sample, to explain this hysteretic behaviour.