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The characterization of high temperature superconductor grain boundary junctions under a magnetic field in the mT range is reported. The devices were obtained by patterning narrow stripes in a YBa2Cu3O7−x (YBCO) film deposited on SrTiO3 and MgO symmetric bi-crystal substrates. To allow the investigation of devices having different current density, two grain boundary disorientations were considered: 24° and 45° for SrTiO3 and 24° for MgO. Current-voltage characteristics as a function of the applied field for several temperatures have been collected. The experimental data are discussed on the basis of the electrical parameters obtained for the different substrates. The periodic modulation of the Josephson critical current with the magnetic field indicates that the behavior of YBCO grain boundary junctions can be approximated by the standard overlap junctions model. A comparison between the experimental variation of the critical current with theoretical behavior allows for the determination of the current de...

Thin layers of YBa2Cu3O7−x (YBCO) deposited on LaAlO3 substrates have been prepared in situ by coevaporation of Y, Ba, and Cu. Incorporation of oxygen was accomplished by an atomic oxygen beam source with high cracking efficiency. The total oxygen flow at the substrate could be kept low enough to permit the use of a quadrupole mass spectrometer for evaporation rate monitoring. Films were strongly c‐axis oriented with rocking curve full width at half‐maximum values of 0.6°. Transport measurements on patterned films yielded critical current densities of 6×106 A/cm2 at 77 K. The deposition method was demonstrated to be feasible for preparation of Y2O3/YBCO heterostructures.