Vortex Pinning Regimes in thin films of YBa2Cu3O7−δ

Abstract

The field dependence of the superconducting current density js(B) and the pinning energy Uc(B) in thin films of YBa2Cu3O7−δ indicates three different pinning regimes. At low fields, μ0H < B* ≈0.7ndφ0 (nd is the density of dislocations), js(B) is constant and Uc = 600K at T = 0 for all YBa2Cu3O7−δ films, independent of the density of dislocvations. This is much lower than the pinning energy of a vortex in a single dislocation, for which Uc ≈ 6000K. At intermediate fields, B* < μ0H < 0.5T, a sharp decreae of Uc is observed. For μ0H> 0.5T, Uc(B) is constant again, with Uc(B) ≈ 80K for sputtered films and Uc(B) ≈ 200K for laser ablated films.