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Maiorov, B., A. V. Silhanek, F. De la Cruz, and E. Osquiguil. "Comment on “strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O7-? single crystals”." Physical Review Letters 88, no. 13 (2002): 1397031.
Abstract: Multiterminal measurements using experimental technique on twinned and untwinned YBa2Cu3O7-? crystals were presented. Inhomogeneous current distribution acting upon an uncorrelated vortex system showed that the dissipation of voltage at the top was larger than at the bottom. The behavior of the current voltage curves showed that the result Vtop = Vbot was a consequence of the limited voltage sensitivity.
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Maiorov, B., A. V. Silhanek, F. De la Cruz, E. Osquiguil, A. Rydh, and Rapp. "Comment on “strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O7-? single crystals” [2] (multiple letters)." Physical Review Letters 88, no. 13 (2002).
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Niebieskikwiat, D., A. Silhanek, L. Civale, G. Nieva, P. Levy, and L. Krusin-Elbaum. "Suppression of matching field effects by splay and pinning energy dispersion in YBa2Cu3O7 with columnar defects." PHYSICAL REVIEW B 63, no. 14 (2001): 144504.
Abstract: 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.
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Silhanek, A., L. Civale, S. Candia, G. Nieva, G. Pasquini, and H. Lanza. "Evidence for vortex staircases in the whole angular range due to competing correlated pinning mechanisms." PHYSICAL REVIEW B 59, no. 21 (1999): 13620–13623.
Abstract: 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].
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