Anisotropy of the flux creep in the motion of vortices along twin-boundary planes in YBa 2 Cu 3 O 7−x single crystals

The anisotropy of the magnetic flux creep in vortex motion parallel to the planes of twin boundaries is investigated experimentally. It is shown that at relatively low magnetic fields the creep velocity is independent of the magnetic field and of the angle α≡∠ H ,ab. It is found that the differential resistivity ρ d ≡dE/dJ tends to saturation at large transport currents, where its value is approximately equal to the viscous drag on vortices in the Bardeen–Stephen model. In low magnetic fields oriented near the ab plane of the crystal the trapping of flux lines between CuO superconducting planes is observed.