Anomalous angular critical current dependences in superconducting multilayered structures

Angular dependences of the critical current density (J(c)(theta)) in superconducting multilayers based on Nb/NbOx were obtained forming an angle with the planar direction. This results from the difficulties of the transition of the flux vortex lattice onto the ground state with minimum energy. As a consequence, the vortex structure depends on the previous field orientations, and thus the rotation leads to the existence of a kink structure even when the magnetic field is parallel to the layers. In accordance with the model, bringing the lattice into the ground state before every measurement at a new angle results in the symmetrical angular dependence of the critical current.