Anisotropic vortex flux behavior in grain-oriented YBa2Cu3O7

Magnetization vector measurements M from field cooled (FC) and zero field cooled (ZFC) states were performed on a grain-oriented YBa2Cu3O7 rotated in fixed magnetic field H initially applied along the c-axis at 4.2K. Our results show that for the low field regime (H=0.5kOe), the vortex flux density B stays close to the ab-plane over a wide range of the rotational angle θ, and associated with a frictional behavior of B relative to the sample rotation in this range of θ. Also, B increases very slowly in this range of θ which means that the initial vortices along the c-axis are strongly pinned inhibiting the creation of more vortices along the ab-plane. For the high field regime, B increases with θ up to 70° and then decreases above this angle. The orientation θB of B relative to H shows two peaks at H=3kOe and another peak for H>4kOe. These peaks shift toward 90° as H is increased. Moreover, as θ exceeds 70° in the range of 70°