MAGNETIC-PROPERTIES IN YBA2CU3O7 SINGLE-CRYSTALS WITH A CROSSED CONFIGURATION OF COLUMNAR DEFECTS

We have studied the magnetic properties of YBa2CU3O7 Single crystals w ith crossed columnar defects of various splay angles (0 degrees simila r to +/-40 degrees). In the temperature range between 50 and 70 K, cry stals with +/-20 degrees show the highest enhancement in J(c) near the matching field of the defect density. We also find that the normalize d creep rates and the vortex, activation energies change with the spla y angle. The relaxation rate for a +/-20 degrees crystal shows the low est value for magnetic fields near the matching field, consistent with the J(c) results. Possible vortex dynamics associated with the crosse d columnar defects are discussed.