Thermally activated flux-flow in epitaxially grown YBa2(Cu1−χZnχ)3O7− thin films

The influence of Zn-impurity atoms on the superconducting critical temperature Tc, the resistive transitions in magnetic fields ϱab(TB, T) and the critical current density jabc(B, T) of epitaxially grown, c-axis oriented YBa2(Cu1−χZnχ)3O7 films is reported. For very small concentrations χ ≤ 0.005 we observe a narrowing of the resistive transitions which leads to a crossing of the depinning lines and corresponds to an enhancement of the average activation energy 〈U〉 by a factor of two. The pinning effectivity of the Zn-dopant atoms can also be deduced from an enhancement of jabc(B, T)/jabc(0, T) in large magnetic fields B ≥ 6T and characteristics features in the angular dependence of jabc(B, T, ϕ) where ϕ is the angle between the external field and the - axis