Magnetostriction relaxation in high- Tc superconductors

Abstract

We have measured magnetostriction in the ab-plane of a single crystal Bi 2Sr 2CaCu 2O 8 platelet sample in external magnetic fields parallel to the c-axis. The hysteresis loops showed very large values for the relative magnetostriction, reaching magnitudes of 10 -4 at LHe temperatures and fields up to 6 T. The qualitative behaviour is well described within a pinning-induced magnetostriction model where the effect resembles a “second order magnetization”. Magnetostriction decay rates were smaller than those seen in complementary magnetization experiments around LHe temperatures. At 15 K the decay is much faster, reflecting a much smaller critical current density that is also verified to decrease with increasing magnetic field; faster at 15 K than at LHe temperatures.