Elucidation of the stable vortex state across the peak effect region in CeRu2

We present magnetization data on a weakly pinned single crystal of CeRu2 sh owing the existence of a stable state of the vortex matter in the peak effe ct (PE) region. The stable state is achieved by cycling the magnetic field by a small amplitude. It is characterized by a unique value of the critical current density, independent of the magnetic history of the sample. The re sults support a recent phenomenological model proposed by Ravikumar et al. [Phys. Rev. B 61 (2000) R6479] which postulates a specific recipe to incorp orate the history dependence of the current density. Our data also shows th e occurrence of a first order phase transition from an ordered vortex phase to a disordered phase across the PE. (C) 2001 Elsevier Science B.V. All ri ghts reserved.