Investigation of coupled DyBa2Cu3O7-(Y1-xPrx)Ba2Cu3O7 multilayer structures

• We report on the behavior of high Tc superconductor coupled multilayer structures in magnetic field perpendicular to the ab plane. In these structures the number N of superconducting layers in the sample has been systematically varied. We extract the activation energy for flux motion from resistive measurements of the superconducting transitions. For samples containing N 24 angstroms thick DyBa2Cu3O7 layers, each separated from the next by 96 angstroms of an (Y0.45Pr0.55)Ba2Cu3O7 alloy, we find that the activation energy U increases linearly with the number N of layers for N < 3 - 4, and then saturates. The linear increase of U is taken as an evidence that coupling through (Y0.45Pr0.55)Ba2Cu3O7 increases the correlated volume involved in the flux motion and thus U. For N = 3 stacked pancake vortices move rigidly and the vortex lattice is 2D. For N > 3 - 4 shear of the vortex lattice becomes important, the vortex lattice dimensionally crosses-over to 3D, and the activation energy saturates.

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NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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