We have studied the activation energy of thermally activated vortex motion using (Pr0.6Y0.4)Ba2Cu3O7/ YBa2Cu3O7/(Pr0.6Y0.4)Ba2Cu3O7 trilayer structures. The dependence of the activation energy on the thickness of the YBa2Cu3O7 layer and magnetic field was studied for YBa2Cu3O7 layer thicknesses of 1.2 ~ 120 nm and fields up to 7 T. We obtain a longitudinal vortex correlation length of 15 ~ 20 nm in YBa2Cu3O7. When the YBa2Cu3O7 layer is a few unit-cells thick, the activation energy shows a logarithmic field dependence. In the thickness range between 10 to 30 nm, the dependence of the activation energy on magnetic field shows a crossover behavior from logarithmic dependence at low fields to one of power law, Uo ~ H-α(with a - 0.5), at high fields. This crossover field does not depend on the thickness of the YBa2Cu3O7 layer.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering