SPATIALLY-RESOLVED OBSERVATION OF STATIC MAGNETIC-FLUX STATES IN YBA2CU3O7-DELTA GRAIN-BOUNDARY JOSEPHSON-JUNCTIONS

With low-temperature scanning electron microscopy, the magnetic flux s tates in high critical temperature Josephson junctions have been image d. The experiments were performed with YBa2Cu3O7-delta thin-film grain boundary Josephson junctions fabricated on [001] tilt SrTiO3 bicrysta ls. For applied magnetic fields parallel to the grain boundary plane, which correspond to local maxima of the magnetic field dependence of t he critical current, the images clearly show the corresponding magneti c flux states in the grain boundary junction. The spatial modulation o f the Josephson current density by the external magnetic field is imag ed directly with a spatial resolution of about 1 micrometer.