Critical current density and flux pinning dominated by neutron irradiation induced defects in YBa2Cu3O7 - x

The functional dependence of critical current density (J_c) upon defect density is studied with neutron irradiation of YBa₂Cu₃O_7-x. Identical polycrystalline samples of YBa₂Cu₃O_7-x have been irradiated with fast neutrons (E≳0.1 MeV) in eight steps between 0 and 2.1 × 10¹⁸ n/cm². Critical current densities are obtained from magnetic hysteresis measurements and correlated with defect density measurements obtained from transmission electron microscopy. We observe that despite the existence of a significant degree of hysteresis in the as grown material the hysteretic J_c in the irradiated samples appears to be dominated by a power law dependence on neutron fluence with an exponent of approximately 1/3 over a wide range of temperature, field and fluence.