Dynamical Properties of Magnetic Flux in High-Tc Oxide Superconductors

The dynamical properties of magnetic flux in high-T
c
oxide superconductors were investigated in magnetic fields of up to 11 kOe by means of torque magnetometry. A discontinuous jump in the magnetic torque was observed when the rotation of a magnet was stopped. The magnetic torque then decreased in proportion to the logarithm of time. The results are interpreted in terms of damping and flux creep effects.