Morphology-dependent intergranular behavior in high-Tc superconducting Y-Ba-Cu-O

Abstract

Isothermal zero-field-cooled magnetization behavior [M(Ha,T)], for increasing applied field Ha in the range 0≤Ha≤Hc1g (where Hc1g is the lower critical field for the Y-Ba-Cu-O grains) and temperatures in the range 69≤T≤Tc, on two polycrystalline untextured Y-Ba-Cu-O specimens of different grain size is compared with a proposed critical-state model. The model assumes a weak-link network of Josephson-coupled grains with a critical current that has two components; a field-independent component [Jc1j(T)] and a field-dependent component [Jc0j(H,T)], which decays exponentially with internal field H over a characteristic range H0(T), which is in turn quantitatively modeled for the weak-link network. The fitting procedure yields the Jcj(0,T) behavior, which is shown to be in agreement over most of the temperature range investigated with a model based on the Ambegaokar-Baratoff theory for a single superconductor-insulator-superconductor Josephson junction modified to include order-parameter suppression in the junction. Near Tc the Jcj(T) behavior of both specimens is shown to be consistent with the Ambegaokar-Halperin theory for thermally activated phase slippage in the Josephson junction. Jc1j is found to scale linearly with Jc0j with a morphology-dependent factor that is independent of temperature. The results of this investigation are discussed in relation to current understanding.

Source-reported materials — not catalogue approval

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