  Superconducting MgB2 strands with nanometer-scale SiC additions have been
investigated systematically using transport and magnetic measurements. A
comparative study of MgB2 strands with different nano-SiC addition levels has
shown C-doping-enhanced critical current density Jc through enhancements in the
upper critical field, Hc2, and decreased anisotropy. The critical current
density and flux pinning force density obtained from magnetic measurements were
found to greatly differ from the values obtained through transport
measurements, particularly with regards to magnetic field dependence. The
differences in magnetic and transport results are largely attributed to
connectivity related effects. On the other hand, based on the scaling behavior
of flux pinning force, there may be other effective pinning centers in MgB2
strands in addition to grain boundary pinning.
