MANIFESTATION OF HISTORY-DEPENDENT CRITICAL CURRENTS VIA DC AND AC MAGNETIZATION MEASUREMENTS IN SINGLE-CRYSTALS OF CERU2 AND 2H-NBSE2

A study of path dependent effects in single crystals of CeRu2 and 2H-N bSe2 shows that critical current density J(c) of the vortex state depe nds on its thermomagnetic history over a very large part of (H,T) para meter space. The path dependence in J(c) is absent above the peak posi tion (i.e., H>H-p) of the peak effect region, which we believe identif ies the complete loss of order in the vortex structure. The highly dis ordered field cooled (FC) state can be healed into a relatively ordere d vortex lattice by subjecting it to a large enough change in de field (few tens of Oe) or by shaking the field cooled state with sufficient ac field (few Oe).