The anomalous mixed state of the C15-Laves phase superconductor CeRu₂: II. History dependence in field-cooled magnetization hysteresis

Abstract

We report an unusual history dependence of the field-cooled magnetization in and around the peak-effect regime of the superconducting mixed state of CeRu₂. Such history effects in magnetization are shown to be absent in the peak-effect regime of the high-T_c superconductor Bi-2212. Some qualitative similarities with and at the same time considerable quantitative differences from relatively old studies of the history dependence of the transport critical current density (J_c) in single-crystal Nb and Nb₃Ge and mo₃Si amorphous films are examined. Our work indicates that the peak effect in CeRu₂ is probably due to a first-order phase transition unlike the peak effect in Bi-2212, and that the latter could be due to a continuous or second-order phase transition. Differences in details of the history effects suggest that the origin of the peak effect in CeRu₂ is likely to be different from those for these hard type-II superconductors.