Statistical studies of the anisotropy of the pinning mechanism in YBaCuO films deposited on polycrystalline YSZ substrates

We have studied the I-V characteristics and the behaviour of the critical current density of YBa2Cu3O7-x films, prepared by sputtering, at different values of applied magnetic field and of temperature. The superconductor was deposited onto polycrystalline ZrO2 (8 mol % Y2O3). The I-V characteristics were obtained by using a short current pulse measurement technique in order to avoid heating phenomena. We have used a theoretical model to describe the I-V characteristics, based on a statistical treatment of the motion of vortices in an arbitrary pinning potential. Besides the determination of the critical current density Jc, this model allows to characterise the pinning sites by a function giving their energetic distribution. In this way we have been able to make a clear distinction between intrinsic and extrinsic pinning in sputtered YBa2Cu3O7-x films. (orig.)