Possible twin-boundary effect upon the properties of high-T_{c} superconductors

Abstract

We have studied the field at which superconductivity nucleates in grain-aligned samples of ${\mathrm{Y}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ very close to the transition temperature ${T}_{c}$. For the field parallel to the c axis and for temperatures within 2 K of ${T}_{c}$, the nucleation field is found to vary as (1-T/${T}_{c}$${)}^{1/2}$. The data suggest that superconductivity localized near twin boundaries may exist at temperatures close to ${T}_{c}$. .AE