Guiding of vortices under competing isotropic and anisotropic pinning conditions: Theory and experiment

摘要

The influence of tailored anisotropic pinning sites on the nonlinear resistivity tensor in the mixed state of epitaxial thin films of niobium was studied by electronic transport measurements and accompanying theoretical modeling. The thin films were prepared by physical vapor deposition of niobium onto faceted a-alumina substrates. The resistivity tensor of the films was determined in the limit of small current densities at various temperatures close to the critical temperature and in different magnetic fields. In these experiments, the angle between the current and the facet ridges of the substrates was set at five fixed angles between 0° and 90°. Perfect guiding of the vortices along the facet ridges was observed over a wide parameter range. The measured resistivities were in good quantitative agreement with the predictions of the employed stochastic modeling approach.