ABSTRACTHigh-energy heavy-ion irradiation has been shown to be effective in introducing flux-pinning defects in Y123 single crystals. Contrary to electron, low energy proton, and fast neutron irradiation, high-energy heavy-ion irradiation produces defects beneficial to flux pinning through the electronic (rather than nuclear) stopping mechanism. This type of stopping results in tubular defects many microns long that can increase the range of irreversible magnetic behavior to higher fields. In contrast, dense arrays of small defects (size < 100 Ang.) produce enhanced critical currents at low fields but do not extend the range of irreversible behavior significantly. We have used two ion-energy combinations in which the electronic stopping powers vary by nearly two orders of magnitude. The difference in stopping powers results in very different defect types, ranging from well oriented and dense (Xe) to much less well oriented and shorter (O) tubular defects. A novel analysis of the ac μ data indicates that the strong pinning introduced by the Xe irradiation breaks the vortex glass picture in favor of an individual pinning model, while O irradiation does not.
