References of "Levy, P"
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See detailSuppression of matching field effects by splay and pinning energy dispersion in YBa2Cu3O7 with columnar defects
Niebieskikwiat, D.; Silhanek, Alejandro ULg; Civale, L. et al

in Physical Review. B : Condensed Matter (2001), 63(14),

We report measurements of the irreversible magnetization M-i of a large number of YBa2Cu3O7 single crystals with columnar defects (CD). Some of them exhibit a maximum in M-i when the density of vortices ... [more ▼]

We report measurements of the irreversible magnetization M-i of a large number of YBa2Cu3O7 single crystals with columnar defects (CD). Some of them exhibit a maximum in M-i when the density of vortices equals the density of tracks, at temperatures above 40 K. We show that the observation of these matching field effects is constrained to those crystals where the orientational and pinning energy dispersion of the CD system lies below a certain threshold. The amount of such dispersion is determined by the mass and energy of the irradiation ions, and by the crystal thickness. Time relaxation measurements show that the matching effects are associated with a reduction of the creep rate, and occur deep into the collective pinning regime. [less ▲]

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See detailThickness effects on the pinning by columnar defects
Silhanek, Alejandro ULg; Guimpel, J.; Civale, L. et al

in Physica C: Superconductivity (2000), 341(Part 2), 1217-1218

We compare the angular dependence of the pinning of equivalent columnar defects in GdBa2Cu2O7 thin films and a thicker YBa2Cu3O7 single crystal. The tracks' related enhancement of the critical currents is ... [more ▼]

We compare the angular dependence of the pinning of equivalent columnar defects in GdBa2Cu2O7 thin films and a thicker YBa2Cu3O7 single crystal. The tracks' related enhancement of the critical currents is much smaller for the case of the thin films. We interpret this thickness dependence as resulting from a competition between the pinning of the correlated structures, related to total sample thickness, and surface boundary conditions, which force the vortices to depin from the columnar defects near the sample surface. [less ▲]

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