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

N. Pompeo; R. Rogai; E. Silva; A. Augieri; V. Galluzzi; G. Celentano

doi:10.1063/1.3056179

paper

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

arXiv:0811.2351 · doi:10.1063/1.3056179

Abstract

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 YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ thin films, where sub-micrometric BaZrO $_{3}$ particles have been incorporated. As a function of the BaZrO $_{3}$ content, we observe that the absolute losses slightly decrease up to a BaZrO $_{3}$ content of 5%, and then increase. We found that the magnetic-field-induced losses behave differently, in that they are not monotonic with increasing BaZrO $_{3}$ concentration: at small concentration (2.5%) the field-induced losses increase, but large reduction of the losses themselves, by factors up to 3, is observed upon further increasing the BaZrO $_{3}$ concentration in the target up to 7%. Using measurements of both surface resistance and surface reactance we estimate vortex pinning-related parameters. We find that BaZrO $_{3}$ inclusions introduce deep and steep pinning wells. In particular, the minimum height of the energy barrier for single vortices is raised. At larger BaZrO $_{3}$ content (5% and 7%) the phenomenon is at its maximum, but it is unclear whether it shows a saturation or not, thus leaving room for further improvements.

arXiv comment7 pages, 7 figures

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

Abstract

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