Magnetic forces in thallium- and bismuth-based superconductors

Hysteretic force-separation relations for Tl, Bi and Y based superconductors and a magnet are compared. The magnitudes of the forces, the hysteresis, and the magnetic stiffness were all largest in the three-layer Tl₂Ba₂Ca₂Cu₃O_x compound, indicating strong flux pinning. The hysteresis in both two and three layer thallium compounds was sufficient to generate attractive forces as the superconductor and magnet were moved apart. The use of remanent fields to improve stability of levitated and suspended magnets is described.