We have observed anomalous magnetization hysteresis (virgin curve lying above the return leg and formation of a knot in the hysteresis) in ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{8+\mathit{y}}$ (BSCCO) single crystals between ${\mathit{T}}_{\mathit{c}}$ and ${\mathit{T}}_{\mathit{c}}$-6 K. We present the temperature evolution of this anomalous behavior. We argue that the observed anomaly is the manifestation of the fluctuation phenomena due to the layered structure and high anisotropy of BSCCO crystal.

• Received 30 January 1995

DOI:https://doi.org/10.1103/PhysRevB.52.6215