Strong Reduction of the Field-Dependent Microwave Surface Resistance in YBCO with BaZrO_3 Inclusions

Abstract

We present measurements of the magnetic field dependent microwave surface resistance in laser-ablated YBa${}_2$Cu${}_3$O${}_{7-\delta }$ films on SrTiO${}_3$ substrates. BaZrO${}_3$ crystallites were included in the films using composite targets containing BaZrO${}_3$ inclusions with mean grain size smaller than 1 $\mu$m. X-ray diffraction showed single epitaxial relationship between BaZrO${}_3$ and YBa${}_2$Cu${}_3$O${}_{7-\delta }$. The effective surface resistance was measured at 47.7 GHz for 60$<T<$90 K and 0$<{\mu }_{0}H<$0.8 T. The magnetic field had a very different effect on pristine YBa${}_2$Cu${}_3$O${}_{7-\delta }$ and YBa${}_2$Cu${}_3$O${}_{7-\delta }$/BaZrO${}_3$, while for ${\mu }_{0}H=$0 only a reduction of $T_c$ in the YBa${}_2$Cu${}_3$O${}_{7-\delta }$/BaZrO${}_3$ film was observed, consistent with dc measurements. At low enough $T$, in moderate fields YBa${}_2$Cu${}_3$O${}_{7-\delta }$/BaZrO${}_3$ exhibited an intrinsic thin film resistance lower than the pure film. The results clearly indicate that BaZrO${}_3$ inclusions determine a strong reduction of the field-dependent surface resistance. From the analysis of the data in the framework of simple models for the microwave surface impedance in the mixed state we argue that BaZrO${}_3$ inclusions determine very steep pinning potentials.

LaTeX, 6 pages, 4 figures, uses jpconf.cls and jpconf11.clo class files, talk given at EUCAS 2007, submitted to J. Phys.: Conf. Series

References in corpus (1)

• Strongly Enhanced Current Densities in Superconducting Coated Conductors of YBa2Cu3O7-x + BaZrO3

Cited by in corpus (2)

• Reduction of the field-dependent microwave surface resistance in YBa_2Cu_3O_7 with sub-micrometric BaZrO_3 inclusions as a function of BaZrO_3 concentration
• Effect of nanosize BaZrO3 inclusions on vortex parameters in YBaCuO