Anisotropy of the depinning field and the pinning force density of thin epitaxial YBa 2Cu 3O 7 films

Abstract

Measurements of the depinning field and the critical current density on epitaxially grown c-axis oriented YBa 2Cu 3O 7 films were performed under variation of the angle ϕ between the field direction and the c-axis of the film with high angular resolution (Δ≈0.04). The critical current densities were measured on a 10 μm wide and 100 μm long strip by applying a 1 μV criterion. The dependence j c(ϕ) obtained for low temperatures can be well explained by a model published by Tachiki and Takahashi. For higher temperatures and higher magnetic fields additional structures appear. The measured angular dependence of the depinning field shows a cusp for ϕ=90°. The complete angular dependence B dp(ϕ) can be explained by simply taking into account the anisotropy of the upper critical field.