Vortex dynamics in YBaCuO single crystals with point- and line-like defects-flux creep studies

Studies of vortex dynamics and pinning were conducted in irradiated Y₁Ba₂Cu₃O₇ single crystals by observing the decay of supercurrents with time. The materials contained either point-like defects from proton irradiation or line-like defects from irradiation with energetic heavy ions. Analysis of the first case gives clear support for collective creep theory. With linear defects, the experiments give evidence for thermal smearing of the vortex pinning potential at higher temperatures, as predicted theoretically.     

Irradiation-induced segregation and diffusion of manganese implants in nickel

The effects of radiation-induced solute redistribution and diffusion are studied for 30 keV Mn implants in nickel irradiated with 75 keV Ni⁺ ions at 500°C. The peak of the Mn implant profile is driven to greater depth with increasing irradiation dose until a steady-state solute profile is established. The rate of drift of Mn atoms and their diffusion coefficient is related to the distribution of point-defects in the nickel under irradiation.     

Vortex motion through the splayed configurations of columnar defects

We report large current enhancements inY Ba ₂ Cu ₃ O _7-σ with splayed columnar defects. An optimalrelative splay angle is Θ _opt = 10° for the planar splay distribution. The vortex motion through gaussian splay appears to be controlled by the large-angle tails of the distribution. The regimes are observed where vortex motion isenhanced rather thansuppressed by splay. The work of V.M.V. and G.K.L. was supported by the U.S. Department of Energy, BES-Material Sciences, under contract W-31-109-Eng-38. We thank J. Hardy and J. Forster at TASCC-Chalk River, supported by AECL Research, for their help and the provision of irradiation facilities.