Damping of the oscillations of a permanent magnet levitating between high-<i>T</i> <i>c</i> superconductors

Abstract

A permanent magnet (spherical shape, radius 100 μm) is levitating inside a superconducting parallel plate capacitor made of YBCO. Translational oscillations of the magnet at its resonance frequency (∼150 Hz) can be excited and detected. The damping of the oscillations is investigated as a function of temperature and oscillation amplitude. Close to Tc we observe a steep minimum of the damping. The data can be described by a linear frictional force which decreases near Tc, and a quadratic one which diverges at Tc. These frictional forces are attributed to flux flow phenomena in the high-Tc superconductor.