Ni-doped epitaxial thin ${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Ni}}_{\mathit{x}}$${)}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ films have been prepared by high-oxygen-pressure dc sputtering from stoichiometric targets on ${\mathrm{SrTiO}}_3$ substrates. Structural properties of these c-axis-oriented films were not affected by Ni doping up to x=15%. Inductively measured transition temperatures show a decrease with a rate of -4.5 K/(at. % Ni) for Ni concentrations up to x=4%. For higher Ni contents the ${\mathit{T}}_{\mathit{c}}$-depression rate changes to -1.5 K/(at. % Ni). A change in slope is also detectable in the dependence of the resistivity on Ni concentration. These results can be explained in a model based on a concentration-dependent site preference of the Ni atoms. The activation energy for vortex creep (extracted from resistive transitions) and the critical-current density show the pinning effectiveness of the dopant. Scaling laws for the pinning-force density have also been studied. The Hall concentration ${\mathit{n}}_{\mathit{H}}$ shows a slight increase for small x and a decrease for higher values. The slope ${\mathit{dn}}_{\mathit{H}}$/dT is also lowered for increasing Ni content. Furthermore, the mobility and the Hall angle of the ${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Ni}}_{\mathit{x}}$${)}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ films were deduced from experimental data.

• Received 14 January 1993

DOI:https://doi.org/10.1103/PhysRevB.47.15185