TEM study of flux pinning defects in YBa2Cu3O7-delta produced by 580 MeV Sn ion irradiation

Recent studies of high T(sub c) superconductors irradiated with high energy heavy ions have indicated that a defect structure is produced which is extremely effective in pinning magnetic flux lines. In attempting to develop models to account for these observations, it is imperative to have a complete characterization of the defects responsible for the property enhancements. Hence, the defect microstructure produced in single crystal YBCO by 580 MeV Sn(sup 30+) irradiation, recently demonstrated to provide highly effective flux pinning at high fields and temperatures, was investigated by conventional transmission electron microscopy. This irradiation condition is shown to produce linear, yet segmented, tracks of damaged material, approximately aligned with the incident irradiation direction, throughout the entire crystal thickness of 22 microns. The cross sectional density of damage tracks is in close agreement with the ion fluence. Two specific characteristics of the track morphology were studied, namely, their continuity and angular spread. The continuity of the tracks does not appear to follow threshold-like behavior within the electronic loss range studied here and the angular distribution of the defect track directions is only approximated by the Monte Carlo calculations of TRIM.