Magnetization studies of the influence of fast neutron irradiation on critical current density of melt-textured YBa₂Cu₃O _7-x

The decrease of the magnetization hysteresis loop proportional to the decrease of the sample size was found for unirradiated and fast neutron irradiated bulk samples obtained from a powder melting process (PMP). This fact indicates that the superconducting current flows throughout the whole sample even when the magnetic field is applied. Thus, the critical current is not limited by field induced decoupling of the weak links. This is a consequence of specific microstructure of PMP samples. The increase of the critical current density by the factor of about 3 was observed after irradiation in magnetic field of 1 T in the examined temperature range from 60 to 85 K. The highest critical current density of the irradiated sample determined from magnetic measurements was equal to 5×10⁴ A/cm² in 1 T at 77 K.