EVIDENCE OF STRONG PINNING IN PERITECTIC GROWN YBA2CU3O7-X SINGLE-CRYSTALS

Large single crystals of YBa2Cu3O7-x are grown by a peritectic growth mechanism. Electron probe microanalysis and SEM show a high density of crystal defects. Magnetization loops measured with a vibrating sample magnetometer are used for the estimation of the anisotropic critical current densities. Peritectically grown crystals show higher critical current densities with smaller anisotropy than eutectically grown crystals. The logarithmic decay of the magnetization with time indicates deeper pinning potentials. These results are confirmed by torque measurements showing a large irreversible isotropic contribution and reduced peaks due to twin boundaries.