Vortex channeling along twin planes in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$

We have studied the magnetic hysteresis of twinned and detwinned ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ single crystals. Our results show that channeling of vortices occurs and that it decreases vortex pinning in the field region near the peak in the hysteresis width. We demonstrate that the effect of the twin planes cannot simply be described in terms of enhanced pinning within the twin planes. By varying the angle of the twin planes with the magnetic field we have found that vortices lock in to the twin planes and an upper bound on the lock-in angle of 3.5° at 60 K has been obtained.