Initial magnetization curve and weak-link properties in Ag2O-doped LaBa2Cu3O7-y.

Abstract

Low-field (0--10 mT) magnetization hysteresis curves which are related to the weak-link properties have been investigated in the ${\mathrm{Ag}}_{2}$O-doped ${\mathrm{LaBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{y}}$ system. A kink anomaly is observed in the initial magnetization curve at a certain field ${\mathit{H}}^{\mathrm{*}}$ less than 1 mT. It is neither a lower critical field of the weak-link region ${\mathit{H}}_{\mathit{c}1\mathit{j}}$ nor a critical field for flux entry at sample surface ${\mathit{H}}_{\mathrm{en}}$. Sample thickness dependence of the irreversible magnetization width \ensuremath{\Delta}M and field sweep width dependence of the hysteresis loss Q suggest a relationship between the kink anomaly and the maximum applied field ${\mathit{H}}_{\mathit{e}}$ which can be screened at the midplane of the thin plate samples in the framework of the Bean's critical-state model.