Rich Behavior of the Critical Currents of Magnetically-Doped Superconducting Films in Applied Magnetic Fields*

Films of MoGe were grown with varying dopant levels of cobalt contamination. Critical currents were measured in the presence of magnetic fields applied parallel to the film plane and perpendicular to current flow. Critical current curves reveal significantly different behavior depending on the polarity of the current with respect to the applied field. At sufficiently-high dopant concentrations, the critical current increases with increasing magnetic field intensity for one polarity of current. We will discuss these results in terms of pair-breaking effects of magnetic fields and magnetic impurities.