Critical scaling behavior of I-V curves inYBa2Cu3O7/PrBa2Cu3O7multilayers

Abstract

The current-voltage (I-V) curves were measured for ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (24 \AA{})/${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (12 \AA{} and 96 \AA{}) multilayers. The measurements were performed in magnetic fields H up to 10 T with various orientations against the film surface and at temperatures well below the superconducting transition temperature. From the critical scaling analysis, the vortex-glass phase transition temperature ${\mathrm{T}}_{\mathrm{g}}$, and critical exponents z and \ensuremath{\nu} were extracted. We found that these parameters depend on the thickness of ${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ layers, magnetic fields, and their orientations. For ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (24 \AA{})/${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (12 \AA{}) multilayers, in the high field (H>1 T) the exponents (z\ensuremath{\sim}4.0--6.0, \ensuremath{\nu}\ensuremath{\sim}1.1--1.7) are basically consistent with the theoretical estimates of a three-dimensional vortex-glass transition, while for ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (24 \AA{})/${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (96 \AA{}) multilayers, when H\ensuremath{\Vert}c, the critical scaling behavior is nearly consistent with that of a quasi-two-dimensional system at H=10 T. Comparing with single-layer ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ thin films with thickness >1000 \AA{}, we found that a size effect on the vortex-glass transition in multilayers exists.