Comparative study of the peak effect in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ single crystals by transport and magnetic measurements

The peak effect in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ single crystals is observed by transport-current measurements. Comparison with the shielding current from magnetization shows good agreement between the results, which exclude granularity as being necessarily involved in the origin of the peak effect. The behavior of the current-voltage characteristics in a wide voltage range (${10}^{\mathrm{-}9}$<E<${10}^{\mathrm{-}4}$ V/cm) is analyzed. Different types of scaling are established in magnetic fields below and above the position of the current peak. Possible mechanisms responsible for the peak effect are discussed.