Periodic oscillations of Josephson-vortex flow resistance in oxygen-deficient YBa2Cu3Ox

We measured the Josephson vortex flow resistance as a function of magnetic field applied parallel to the ab planes using annealed YBa2Cu3Ox intrinsic Josephson junctions having high anisotropy (similar to 40) by oxygen content reduction. Periodic oscillations were observed in magnetic fields above 45-58 kOe, corresponding to dense-dilute boundary for Josephson vortex lattice. The observed period of oscillations, which agrees well with the increase of one fluxon per two junctions (H-p=Phi(0)/2Ls), may correspond to formation of a triangular lattice of Josephson vortices as has been reported by Ooi for highly anisotropic (>= 200) Bi-2212 intrinsic Josephson junctions.