AC Susceptibility of YBa2Cu3O7-δ Single Crystals

S. II. Chun ； H. J. Lee ； Z. G. Khim

《Chinese Journal of Physics》 36卷2S期 (1998/04) Pp. 302-310

並列摘要

We studied the mixed state ac response of a twinned YBa2Cu3O7-δ single crystal. We observed a dip structure in real part and a sharp peak in the imaginary part of the ac susceptibility at, a well defined temperature TM. The dc magnetization also shows a kink at the same temperature. These are interpreted as a precursor of the critical current peak effect, whose origin is thought to be the thermal softening of the elastic moduli as the flux line lattice melts. The peak effect is accompanied by an unexpected magnetic history dependence of the ac susceptibility between 50 K and TM, which is interpreted as the indication of flux line defects. The anomalous X falls on an universal X' - X'' curve, which is different from either the diffusion model or the Bean model. The peak position agrees with the reported first order melting line and thus might be the onset temperature of plastic motion of flux line lattice.