Grain boundary junctions of FeSe0.5Te0.5 thin films on SrTiO3 bi-crystal substrates

degrees Grain boundary junctions were fabricated in the epitaxial FeSe0.5Te0.5 thin films on [001] tilt SrTiO3 bi-crystal substrates with a CeO2 buffer layer. Critical current densities across the junctions with different mis-orientation angles of 4 degrees, 7 degrees, 15 degrees, and 24 degrees were measured at magnetic fields up to 30 T. It was found that the 4 degrees and 7 degrees junctions carry critical current densities comparable to that of the intra-grain film while those of the 15 degrees and 24 degrees junctions were suppressed drastically. A critical mis-orientation angle of around 9 degrees was identified that separates the strong coupling region from the weak link region. We found that the critical current densities across the grain boundary with a 24 degrees mis-orientation angle are modulated by the magnetic field, indicating a Josephson Effect. This junction is estimated to be in the intermediate-size regime with an effective transverse junction width L similar to 2.6-2.8 mu m and a Josephson penetration depth lambda(J) similar to 1.2 mu m. (C) 2015 AIP Publishing LLC.