Enhancements of the critical currents of YBaCuO single crystals by neutron (n) and proton (p) irradiation

The results of magnetization hysteresis and T/sub c/ measurements on neutron- and proton-irradiated YBaCuO single crystals are presented. The crystals used for comparison were irradiated to a fluence of 2*10/sup 17/ n/cm/sup 2/ (E>0.1 MeV) and 1*10/sup 16/ p/cm/sup 2/ (E=3.5 MeV). The critical currents at 1 T and 10 K are enhanced by a factor of five for the neutron-irradiated and a factor of nine for the proton-irradiated samples. After irradiation the crystals were annealed at 100, 200 and 300 degrees C for 8 h each in air. Following each annealing step the critical temperature and the magnetization hysteresis at 10 and 70 K were measured. Upon annealing, a decrease of the critical currents, which is more pronounced for the proton irradiated sample, is observed. This decrease is related to the removal of point defects or their small clusters. Thus, their contribution to pinning can be studied. The critical temperature decreases after both types of irradiation by about 0.5 K and is fully recovered after annealing.<>