Directional pinning and anisotropy in YBa2Cu3O7−x with BaZrO3 nanorods: Intrinsic and nanorods-induced anisotropy

We present a study of the anisotropic vortex parameters as obtained from measurements of the microwave complex resistivity in the vortex state with a tilted applied magnetic field in YBa2Cu3O7−x thin films with BaZrO3 nanorods. We present the angular dependence of the vortex viscosity η, the pinning constant kp and the upper limit for the creep factor χM. We show that the directional effect of the nanorods is absent in η, which is dictated by the mass anisotropy γ. By contrast, pinning-mediated properties are strongly affected by the nanorods. It is significant that the pinning and creep affected by the nanorods is detectable also at our very high operating frequency, which implies very short-range displacements of the vortices from their equilibrium position.