OXYGEN DISPLACEMENT IN A AG-107(17-IRRADIATED BI2SR2CACU2O8 SINGLE-CRYSTAL() ION)

We have studied the magnetic field (H parallel to c) dependent rf diss ipation (H-r parallel to a) in an as-grown Bi2Sr2CaCu2O8 single crysta l prior to and after irradiation with 250 MeV Ag-107(17+) ions. In a c omparison of the responses from the as-grown crystal with an air-annea led crystal, features due to oxygen deficient regions acting as weak l inks in the former are identified. These features disappear immediatel y after irradiation of the as-grown crystal. We attribute such behavio r to the displacement of oxygen from columnar tracks to deficient regi ons thus eliminating the weak links. Losses from the same irradiated a s-grown crystal stored at 300 K for 60 days show that the features sim ilar but not identical to those observed in the pristine state have re appeared implying that the displaced oxygen is in a metastable configu ration in the deficient regions and hence is mobile due to thermal eff ects even at 300 K. (C) 1997 American Institute of Physics.