Flux pinning in YBa2Cu3O7-x single crystals for magnetic field oriented parallel and perpendicular to the CuO2 planes

Flux pinning properties of YBa2Cu3O7-x Single crystals have been studied fo r external magnetic field oriented both parallel and perpendicular to the C uO2 planes (ab-planes). For H parallel to ab, dynamic vortex behavior is ma inly determined by a very effective intrinsic pinning mechanism. For H para llel to c, we observe the "fishtail effect" in the M(H) behavior, over a ve ry broad temperature range. For N parallel to ab, this effect is observed o nly at temperatures very close to T-c, where the intrinsic pinning contribu tion is much weaker. However, analysis of the pinning force indicates that the same type of defects is responsible for the fishtail effect for both ma gnetic field orientations. (C) 2000 Elsevier Science B.V. All rights reserv ed.