Electrical transport properties influenced by surface barriers in a high-Tc superconducting strip

In order to characterize electrical transport properties influenced by surface barriers (SBs) in high-Tc superconductors with narrow widths under magnetic fields (H) along the crystal c-axis, we have investigated the properties of individual Bi2Sr2CaCu2O8+δ whiskers with different widths at a high temperature and low-field region. Nonmonotonic field dependence of critical current density (Jc) along the a-axis, i.e., a peak effect in Jc(H), occurs in a low-field regime below 100 Oe. In addition, the peak effect is indicated by the variation of voltage under bias current along the a-axis with increasing and decreasing fields. The field (Hpeak) at which a peak in Jc appears systematically increases with decreasing sample width. The size effect on Hpeak suggests that the peak effect observed in the whiskers is attributed to increasing the correlation between vortices confined by SBs in the finite narrow width with an increase in field.