Magnetic irreversibility in (Hg1−xRex)Ba2Ca2Cu3O8+δ: effects of neutron irradiation

We studied the intragrain magnetic hysteresis of the superconductor (Hg 1− x Re x )Ba 2 Ca 2 Cu 3 O 8+ δ ( x =0.10, 0.18 and 0.25) close to T c . From the magnetization curves we determined the temperature dependence of the irreversibility field ( H irr ( T )), and the field dependence of the magnetization curve width ( ΔM ( H )). After irradiation to a fluence of 2×10 21 m −2 ( E >0.1 MeV), the magnetization curves moderately increase their symmetry, and sizeable enhancements of H irr ( T ) and ΔM ( H ) are observed. Although the substitution x =0.18 shows the best pinning properties before irradiation, x =0.10 matches—or even surpasses—them afterwards. This suggests that, within our temperature and field window, neutron irradiation plays a far more important role than Re-substitution in enhancing the irreversible behavior in the Hg-1223 system.