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The introduction of artificial pinning sites in YBa2Cu3O7-δ (YBCO) epitaxial thin films has been obtained by pulsed laser deposition (PLD) technique from YBCO-BaZrO3 (BZO) composite targets with BZO concentration ranging from 2.5 to 7 mol %. The typical critical temperature, Tc, drop observed in YBCO-secondary phase films grown by PLD has been successfully recovered by increasing the deposition temperature. Transport properties analyses revealed improved pinning force values for YBCO-BZO films for BZO concentration above 5 mol %. These films exhibited an anomalous dual peak structure which has been ascribed to the presence of two pinning contributions. The crossover field, Bm, separating these two pinning regimes has been observed to be temperature independent suggesting the occurrence of the matching field effect. The measured value of Bm agreed with the matching field value, B[uppercase_phi_synonym]=Knd[uppercase_phi_synonym]0, as evaluated from transmission electron microscopy investigations. The mark of this phenomenon is retained down to 10 K, making YBCO-BZO more performing than pristine YBCO films at applied magnetic fields below Bm in all the temperature range inspected. On the contrary, in the high magnetic field range (above Bm), the effectiveness of correlated pinning is progressively reduced on lowering the temperature suggesting that at low temperatures the dominant pinning contribution arises from isotropic pinning centers. [ABSTRACT FROM AUTHOR]

In order to study the vortex pinning determined by artificially introduced pinning centers in the small-vortex displacement regime, we measured the microwave surface impedance at 47.7 GHz in the mixed state of YBa2Cu3O7-δ thin films, where submicrometric BaZrO3 particles have been incorporated. As a function of the BaZrO3 content, we observed that the absolute losses slightly decrease up to a BaZrO3 content of 5%, and then increase. We found that the magnetic-field-induced losses behave differently in that they are not monotonic with increasing BaZrO3 concentration. At small concentration (2.5%) the field-induced losses increase, but large reduction in the losses themselves, by factors up to 3, is observed upon further increasing the BaZrO3 concentration in the target up to 7%. Using measurements of both surface resistance and surface reactance, we estimate vortex pinning-related parameters. We found that BaZrO3 inclusions introduce deep and steep pinning wells. In particular, the minimum height of the energy barrier for single vortices is raised. At larger BaZrO3 content (5% and 7%) the phenomenon is at its maximum, but it is unclear whether it shows a saturation or not, leaving room for further improvements. [ABSTRACT FROM AUTHOR]

In this paper, we present a detailed investigation of the self-field transport properties of an ionic liquid gated ultra-thin YBa2Cu3O7-x (YBCO) film. From the high temperature dynamic of the resistivity (>220 K), different scenarios pertaining to the interaction between the liquid and the thin film are proposed. From the low temperature evolution of Jc and Tc, a comparison between the behavior of our system and the standard properties of YBCO is drawn. [ABSTRACT FROM AUTHOR]

Pulsed laser deposited thin YBa2Cu3O7-x (YBCO) films with pinning additions of 5 at. % Ba2YTaO6 (BYTO) were compared to films with 2.5 at. % Ba2YTaO6 + 2.5 at. % Ba2YNbO6 (BYNTO) additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO) and 11 T (YBCO-BYNTO), representing the highest ever achieved values in YBCO films. [ABSTRACT FROM AUTHOR]

We observe a strong reduction of the field induced thin film surface resistance measured at high microwave frequency (ν=47.7 GHz) in YBa2Cu3O7-δ thin films grown on SrTiO3 substrates, as a consequence of the introduction of submicrometric BaZrO3 particles. The field increase of the surface resistance is smaller by a factor of ∼3 in the film with BaZrO3 inclusions, while the zero-field properties are not much affected. Combining surface resistance and surface reactance data, we conclude (a) that BaZrO3 inclusions determine very deep and steep pinning wells and (b) that the pinning changes nature with respect to the pure film. [ABSTRACT FROM AUTHOR]

Measurements of anisotropic transport properties (dc and high-frequency regime) of driven vortex matter in YBa2Cu3O7-x with elongated strong-pinning sites (c-axis aligned, self-assembled BaZrO3 nanorods) are used to demonstrate that the effective-mass angular scaling takes place only in intrinsic physical quantities (flux-flow resistivity), and not in pinning-related Labusch parameter and critical currents. Comparison of the dynamics at different time scales shows evidence for a transition of the vortex matter toward a Mott phase, driven by the presence of nanorods. The strong pinning in dc arises partially from a dynamic effect. [ABSTRACT FROM AUTHOR]