Simulation of magnetic relaxation measurements of tetragonal Bi2Sr2CaCu2O8+x and Bi2Sr2Ca2Cu3O10+y thin films

Magnetic relaxation data at various temperatures and magnetic fields are taken from high-quality, epitaxial thin films of and and are simulated using a method developed by Brandt and coworkers. Assuming thermally activated resistivity and logarithmic activation energy we obtain good simulations of the experimental data. The critical current resulting from the simulation is evaluated as a function of the temperature and is found to decrease linearly with it and the current-voltage characteristics are extracted and are linear on a scale at all temperatures. The activation energy is calculated as a function of the current and it is shown to be a decreasing function of the magnetic field following a power law . The critical current is also shown to decrease with the magnetic field and can be described well by the exponential form . Comparison between the two phases and indicates that pinning in the film is stronger due to the lower anisotropy of this phase and probably because of the existence of more defects. Finally, the distribution of the local magnetic moment and the magnetic induction on the surface of the film at different times during the relaxation procedure is nicely depicted with surface and contour plots