Vortex dynamics in Bi2Sr2CaCu2O8-thin films in the presence of columnar defects

With heavy ion irradiation we create continous amorphous columnar defects in Bi2Sr2CaCu2O8-thin films. With regard to a reliable comparison of irradiation effects three of four identical striplines on the same samples were exposed to different irradiation procedures. We performed irradiations as well parallel as under different angles with respect to the film $$\vec c$$ -axis. Beside an enlarged normal state resistivity after irradiation the films suffer a Tc-reduction proportional to the volume of the damaged material. The activation energy ascertained from resistive transitions shows best enhancement for magnetic field values close to the matching field. Measurements of the transport crit…

Finite range scattering of Ni and Zn impurities in Y-123 thin films

Abstract We investigated YBa 2 (Cu 1− z M z ) 3 O 7-δ (M Ni,Zn) thin films and determined the decrease of T c and the increase of residual resistivity due to Cu-site substitution, taking into account the CuO-chain contributions to the total conductivity. Although Zn suppresses T c stronger than Ni by a factor of 2.3 the increase of resistivity differs only slightly. Furthermore the observed resistivities are too high to be explained within scattering from point-like defects. To reconcile these contradictions, we assumed finite size scattering potentials, which lead to scattering phase shifts δ l of higher angular momebtum l > 0. T c -suppression is discussed qalitatively within this picture.

Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCu2O8+δfilms

The supercurrent transport properties of epitaxial ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ films in zero applied magnetic field were investigated in a temperature interval of \ensuremath{\approx}20 K below the mean-field critical temperature ${T}_{c0}.$ The modification of the shape of the $I\ensuremath{-}V$ curves observed by varying the temperature was explained in terms of vortex-fluctuation-induced layer decoupling and vortex-antivortex unbinding, revealing a strong probing-length dependence. The change of the effective dimensionality of thermally excited vortices involved in the dissipation process leads to the appearance of …

Flux-flow instability and its anisotropy inBi2Sr2CaCu2O8+δsuperconducting films

We report measurements on voltage instability at high flux-flow velocities in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ superconducting films. Current-voltage $(I\ensuremath{-}V)$ characteristics have been measured as a function of temperature, magnetic field, and angle between the field and the c axis of the sample. Voltage jumps were observed in $I\ensuremath{-}V$ characteristics taken in all magnetic-field directions and in extended temperature and field ranges. An analysis of the experimental data, based on a theory for viscous flux-flow instability with a finite heat-removal rate from the sample, yielded the inelastic scatterin…

Flux Pinning by Columnar Defects in Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8</sub>-Thin Films

Absence of correlated flux pinning by columnar defects in irradiated epitaxial Bi2Sr2CaCu2O8 thin films

Abstract Using heavy-ion irradiation, we produced columnar defects of different density and orientation in epitaxial Bi 2 Sr 2 CaCu 2 O 8 thin films. Although this increases the normal state resistivity and the critical temperature is reduced proportionally to the volume fraction of damaged material, pinning-related quantities like critical current density, activation energy and depinning field are enhanced in external magnetic fields. Transport measurements in dependence of the magnetic field and its orientation consistently indicate two-dimensional pinning of pancake vortices at the columnar defects. We observe the absence of correlated flux pinning by columnar defects and compare to heav…