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See detailIrreversible magnetization under rotating fields and lock-in effect on a ErBa2Cu3O7-delta single crystal with columnar defects
Avila, M. A.; Civale, L.; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2001), 64(14),

We have measured the irreversible magnetization (M-i) of an ErBa2Cu3O7-delta single crystal with columnar defects (CD), using a technique based on sample rotation under a fixed magnetic field H. This ... [more ▼]

We have measured the irreversible magnetization (M-i) of an ErBa2Cu3O7-delta single crystal with columnar defects (CD), using a technique based on sample rotation under a fixed magnetic field H. This method is valid for samples whose magnetization vector remains perpendicular to the sample surface over a wide angle range-which is the case for platelets and thin films-and presents several advantages over measurements of M-L(H) loops at fixed angles. The resulting M-i(Theta) curves for several temperatures show a peak in the CD direction at high fields. At lower fields, a very well defined plateau indicative of the vortex lock-in to the CD develops. The H dependence of the lock-in angle phi (L) follows the H-1 theoretical prediction, while the temperature dependence is in agreement with entropic smearing effects corresponding to long range vortex-defects interactions. [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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See detailEvidence for vortex staircases in the whole angular range due to competing correlated pinning mechanisms
Silhanek, Alejandro ULg; Civale, L.; Candia, S. et al

in Physical Review. B : Condensed Matter (1999), 59(21), 13620-13623

We present measurements of the angular dependence of the irreversible magnetization of YBa2Cu3O7 single crystals with columnar defects inclined with respect to the c axis. At high fields a sharp maximum ... [more ▼]

We present measurements of the angular dependence of the irreversible magnetization of YBa2Cu3O7 single crystals with columnar defects inclined with respect to the c axis. At high fields a sharp maximum centered at the tracks direction is observed. At low fields we identify a lock-in phase characterized by an angle-independent pinning strength and observe an angular shift of the peak towards the c axis that originates in the misalignment between vortices and applied field in anisotropic materials. The interplay among columnar defects, twins, and intrinsic pinning by the ab planes generates a variety of staircase structures. We show that correlated pinning dominates for all orientations of the applied field. [S0163-1829(99)09417-5]. [less ▲]

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