Effect of the misorientation angle on the magnetic properties of YBCO grain boundary Josephson junctions

We have studied magnetic properties of YBa/sub 2/Cu/sub 3/O/sub x/ grain boundary Josephson junctions (GBJJs) fabricated on SrTiO/sub 3/ bicrystal substrates to investigate whether the Josephson characteristics change or not owing to the variation of the misorientation angle. When the misorientation angle was 36.8/spl deg/, the total current was periodically suppressed by the applied field; the current component was almost Josephson current. On the contrary, for the GBJJs (/spl theta/=24/spl deg/), the n-th minima (n/spl ges/2) in the Ic(B) patterns did not occur at zero; a constant non-Josephson current (bulky supercurrent) contribution to the patterns was present. The results were also identified from the existence of an excess current in the I-V curves (/spl theta/=24/spl deg/) and a residual supercurrent in the strong magnetic field dependence of Ic for the GBJJs with /spl theta/=24/spl deg/ (the field was applied up to 14 T). Next, the junction homogeneity was investigated from the differences between measured Ic(B) patterns and that of an ideal Josephson junction. Contrary to expectation, the deviations of the GBJJs with /spl theta/=24/spl deg/ or /spl theta/=36.8/spl deg/ from an ideal Ic(B) pattern corresponded; the first minima did not occur at zero, then the first maxima occurred at higher values than normalized ideal case (I/sub 1-th minima//Ic/sub MAX//spl ap/0.22). As a result, the current density distribution is considered as an asymmetrical current density profile peaked at the junction edges. Last, we have tried to control Jc on the same tilt angle by changing the laser power in the pulsed laser deposition process. The results showed Jc varied at the range of about two order.<
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