Macrostructure and Diamagnetic Response of YBa ₂ Cu ₃ O _{7- <i>x</i>}

Abstract

The experimental low-frequency magnetic response of Y-Ba-Cu-O sintered samples is astonishingly similar to that of model systems made of weakly coupled classical superconducting grains. A quantitative description of this behaviour in the framework of the coherence transition is given. It allows the extraction of important physical information, like the penetration depth λ(T), and provides explanations for the observed low-field sensitivity and temperature dependence of λ.