Guided vortex motion in dilute strong pinning environment: Models and experiment.

• A brief overview of models predicting guiding angles is given. • The guiding effect has been experimentally studied depending on the magnetic field magnitude and the excitation current on the Nb-Ti tape with rarefied α-Ti particles – strong pinning centers. • The experimental data and models are compared. The model that describes the experiment most accurately is chosen. • It is shown that the guiding experiments can serve as a tool to distinguish between plastic and elastic flux flow modes. This article provides a brief overview of existing models that describe the guided flux motion phenomenon. The first model was proposed by Niessen et al. This original model utilizes the single-vortex approximation and provides a qualitative explanation of the effect; however, in most cases it provides an overestimated guiding angle. A second stochastic model explains the experimentally observed guiding angle decreasing (so-called "slipping effect") by the influence of thermal fluctuations. However, the performed estimations show that thermal fluctuations should not be significant. Another model for predicting the guiding angle is the anisotropic pinning model. This model operates in the critical state approximation, and the slipping effect is the combined action of anisotropic pinning and vortex interaction. The predictions of all three models were experimentally tested on a wide superconducting Nb-Ti tape containing 6% by volume ratio of α-Ti particles that act as strong pinning centers. The number of samples was sliced at different angles to the rolling direction to control the driving force direction with respect to the principal material directions. The transverse and longitudinal components of the electrical field were measured simultaneously in a perpendicular magnetic field with increasing transport current. It was found that when the generated electric field was sufficiently small, the guiding angle varied significantly at different locations along the sample. In this case, the anisotropic pinning model predicted the guiding angle averaged over the sample length. With a further increase in the transport current (and driving force), the guiding angle became uniform along the sample. [ABSTRACT FROM AUTHOR]