AMPLITUDE AND FREQUENCY-DEPENDENCE OF HYSTERESIS LOSS IN A MAGNET-SUPERCONDUCTOR LEVITATION-SYSTEM

Using an electromagnetically controlled mechanical pendulum, we measur ed the energy loss for different amplitudes in a magnetic levitation s ystem that contained high temperature superconductors (HTSs). Two proc edures were followed to measure losses at 77 K for frequencies of 93.8 mHz to 80 Hz. In the first procedure, the distance between the perman ent magnet and the HTS levitator was the same as that during (field) c ooling. In the second procedure, the magnet was towered (after cooling ) closer to the HTS levitator before the measurements were performed. The experimental data show that these two procedures give essentially the same results at the same distance despite different cooling (and m agnetization) histories for melt-textured YBaCuO levitators, and the f requency-independent energy loss is a power-law function of amplitude. We attribute the energy loss to magnetic hysteresis in the supercondu ctor.