Superconductors as Permanent Magnets

A discussion is given concerning the properties of superconductors considered as permanent magnets. Experiments on solid and hollow cylinders of lead are reported and compared to theoretical predictions. A macroscopic theory is developed of the filamentary mesh high-field superconductor in the form of an infinite plate. An experiment on a sample of ${\mathrm{Nb}}_3\mathrm{Sn}$ shows maximum energy product greater than 25 MG-Oe at 4.2°K. The phenomenon of discontinuous flux jumping is demonstrated and discussed briefly.