PROCESSING HIGH-T(C) SUPERCONDUCTORS WITH GEV HEAVY-IONS

Irradiation of high-T(c) superconducting crystals with low doses (10(1 0)-10(11) ions/cm2) of GeV heavy ions produces a unique microstructure consisting of discrete amorphous columns which are only a few nm in d iameter but tens of mum long. It has been found recently that this col umnar microstructure causes larger increases in magnetization and crit ical current at high temperature and high magnetic field than other ty pes of defects in these materials. This can be understood as a consequ ence of the effective pinning of magnetic vortex lines provided by the columnar defects. Measurements confirm that the pinning is strongest when the magnetic field is aligned with the ion tracks. Differences in the pinning in different materials can be related to differences in t heir anisotropy, which affects the structure of the vortices and their pinning at columnar defects.