FLUX MOTION IN TWIN BOUNDARIES OF YBA2CU3OX SINGLE-CRYSTALS

The effect of the twin boundaries on flux motion has been studied by u sing a densely twinned and a perfectly detwinned domain in the same 12 3 single crystal. The most successful detwinning of the 123 crystals w as a thermomechanical treatment under inert gas, which kept the perfec tly detwinned domain after oxygen annealing. The influence of the twin boundaries on flux motion strongly depended on temperature. The prese nce of the twin boundaries brought about a reduction of the flux pinni ng force in low temperature, but with an increase in temperature, the twin boundaries worked as strong pins.