Enhanced levitation forces with field cooled YBa2Cu3O7−δ

We have examined levitation forces of field cooled (2.3 T) and zero field cooled YBa2Cu3O7−δ superconductors opposed by a SmCo magnet. We have achieved unusually large levitation forces (140 N) and pressures (44.6 N/cm2) in field cooled measurements. 5–10 subsequent cycles, of approach and retreat of the magnet, result in a 10–20% decrease in force, which then stabilizes.