Vortex pinning in high-Tc materials via randomly oriented columnar defects, created by GeV proton-induced fission fragments

Abstract

Extensive work has shown that irradiation with 0.8 GeV protons can produce randomly oriented columnar defects (CD's) in a large number of HTS materials, specifically those cuprates containing Hg, Tl, Pb, Bi, and similar heavy elements. Absorbing the incident proton causes the nucleus of these species to fission, and the recoiling fission fragments create amorphous tracks, i.e., CD's. The superconductive transition temperature T c decreases linearly with proton fluence and we analyze how the rate depends on the family of superconductors. In a study of Tl-2212 materials, adding defects decreases the equilibrium magnetization M eq (H) significantly in magnitude and changes its field dependence; this result is modeled in terms of vortex pinning. Analysis of the irreversible magnetization and its time dependence shows marked increases in the persistent current density and effective pinning energy, and leads to an estimate for the elementary attempt time for vortex hopping, 2 ~ 4×10 9 s.

Island growth of Y2BaCuO5 nanoparticles in (211∼1.5 nm/123∼10 nm)×N composite multilayer structures to enhance flux pinning of YBa2Cu3O7−δ films

“…3 compared to a reference 123 film. 28 The J c s of the (211/123)×N composite samples are shown in Fig. A shift of the 00l peaks toward higher 2 values was in general observed by XRD diffraction in Fig.…”

Increase of critical currents and peak effect in Mo-substitutedYBa2Cu3O7

“…1,2,3,4,5,6,7,8 One of the most effective methods of increasing the flux pinning at intermediate range of applied fields is creation of columnar irradiation defects. 9,10,11 Another effective method is introduction of microscopic grains of the Y 2 BaCuO 5 phase that are the most efficient at the intermediate range of temperatures. 2,4 Both these methods are rather difficult to implement in large-scale applications.…”