Pair breaking effects of atomic disorder induced in YBa2Cu3O7 by electron irradiation

Abstract Irradiation effects of electrons at very low temperatures ( T irr K , 2.7 MeV ) on the DC-susceptibility χ DC above T c of YBa 2 Cu 3 O 7 have been studied by means of a SHE SQUID magnetometer. Contrary to nonirradiated stoichiometric samples which have a nearly temperature independent paramagnetic susceptibility, χ DC , between 100°C and 300°C, specimens irradiated with doses of 4 × 10 19 e - /cm 2 show a distinct Curie-type behaviour due to the formation of local magnetic moments, superimposed on a temperature independent part. By annealing up to temperatures of 500 K recovering of the Curie-type contribution takes place in a similar way as that of T c . The Pauli susceptibility remains constant during irradiation, indicating that there is, contrary to A15-superconductors, no significant reduction of the density of states at the Fermi level. The correlated annealing of T c and of the Curie constant suggests a magnetic pair breaking mechanism due to radiation induced local magnetic moment.