Unusually strong coherent response from grain-boundary Josephson network in polycrystalline Pr_{x}Y_{1-x}Ba_2Cu_3O_7

TL;DR

This study reveals strong, coherent Josephson responses in polycrystalline Pr_{x}Y_{1-x}Ba_2Cu_3O_7, demonstrating sharp oscillations due to Josephson vortices, modeled successfully with a Lorentz distribution of junction areas.

Contribution

First observation of sharp Fraunhofer-like oscillations in AC susceptibility of Pr_{x}Y_{1-x}Ba_2Cu_3O_7, indicating coherent Josephson vortex behavior in grain boundaries.

Findings

Detected sharp Fraunhofer oscillations in AC susceptibility.

Modeled data successfully with Lorentz distribution of junction areas.

Confirmed Josephson vortex penetration in grain boundaries.

Abstract

By applying a highly sensitive homemade AC susceptibility technique to Pr_{x}Y_{1-x}Ba_2Cu_3O_7 polycrystals (with x=0.0, 0.1 and 0.3), we observed very sharp Fraunhofer type low-field periodic oscillations of the real part of the AC susceptibility which were attributed to Josephson vortices penetrating intergranular regions of grain-boundary Josephson network in our samples. Assuming the Lorentz type distribution of single-junction contact areas, we were able to successfully fit the experimental data.