Statistical Studies of the Anisotropy of the Pinning Mechanism in YBaCuO Films Deposited on Polycrystalline YSZ Substrates

Abstract
We have studied the I-V characteristics and the behaviour of the critical current density of YBa₂Cu₃O_7-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 J_c, 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 YBa₂Cu₃O_7-xfilms.