No abstract

The London penetration depth, lambda(ab)(T), is reported for thin films of the electron-doped superconductor Pr(2-x)Ce(x)CuO(4-delta) with varying Ce concentration, x=0.13, 0.15, and 0.17. Measurements down to 0.35 K were carried out using a tunnel-diode oscillator with excitation fields applied both perpendicular and parallel to the conducting planes. Films at all three doping levels exhibited power law behavior indicative of d-wave pairing with impurity scattering. These results are fully consistent with previous measurements on single crystals.

Using pulsed-laser ablation with an improved oxygen annealing process and Hall effect measurements, we show that the reduction process needed to induce superconductivity in electron-doped cuprates thin films does not trigger a significant change in carrier concentration ͑or band filling͒ contrary to cerium substitution. We show that it has, however, a severe impact on hole-type carrier mobility. This feature is evidenced by focusing on the overdoped regime ͑x Ն 0.16͒ for which reduction increases the contributions of hole-type quasiparticle excitations to the Hall coefficient without affecting much the contribution from electrons. Since reduction has been also shown recently to provoke a strong suppression of antiferromagnetic order for doping close to optimal, we interpret the strong increase in mobility to result from a decreasing scattering rate related to a decreasing strength of antiferromagnetic correlations. We suggest that delocalization of hole-type carriers with reduction is achieved through the frustration of the antiferromagnetic order of as-grown nonsuperconducting composition by in-plane oxygen vacancies. We propose a comparison of ARPES data for as-grown and reduced Pr 2−x Ce x CuO 4 on the overdoped side as a possible experiment to clarify the origin of the hole-type quasiparticles with reduction.

Using magnetoresistance measurements as a function of applied magnetic field and its direction of application, we present sharp angular-dependent magnetoresistance oscillations for the electrondoped cuprates in their low-temperature non-metallic regime. The presence of irreversibility in the magnetoresistance measurements and the related strong anisotropy of the field dependence for different in-plane magnetic field orientations indicate that magnetic domains play an important role for the determination of electronic properties. These domains are likely related to the stripe phase reported previously in hole-doped cuprates.