Critical scaling behavior of I-V curves in YBa2Cu3O7/PrBa2Cu3O7 multilayers

The current-voltage (I-V) curves were measured for YBa2Cu3O7 (24 Angstrom)/PrBa2Cu3O7 (12 Angstrom and 96 Angstrom) 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 T-g, and critical exponents z and v were extracted. We found that these parameters depend on the thickness of PrBa2Cu3O7 layers, magnetic fields, and their orientations. For YBa2Cu3O7 (24 Angstrom)/PrBa2CU3O7 (12 Angstrom) multilayers, in the high field (H > 1 T) the exponents (z similar to 4.0-6.0, v similar to 1.1-1.7) are basically consistent with the theoretical estimates of a three-dimensional vortex-glass transition, while for YBa2Cu3O7 (24 Angstrom)/PrBa2CU3O7 (96 Angstrom) multilayers, when H parallel to c, the critical scaling behavior is nearly consistent with that of a quasi-two-dimensional system at H = 10 T. Comparing with single-layer YBa2CU3O7 thin films with thickness > 1000 Angstrom, we found that a size effect on the vortex-glass transition in multilayers exists.