Manifestation of history-dependent critical currents via dc and ac magnetization measurements in single crystals of CeRu₂ and 2H-NbSe₂

Abstract

A study of path dependent effects in single crystals of CeRu₂ and 2H-NbSe₂ shows that critical current density J_c of the vortex state depends on its thermomagnetic history over a very large part of (H,T) parameter space. The path dependence in J_c is absent above the peak position (i.e., H>H_p) of the peak effect region, which we believe identifies the complete loss of order in the vortex structure. The highly disordered field cooled (FC) state can be healed into a relatively ordered vortex lattice by subjecting it to a large enough change in dc field (few tens of Oe) or by shaking the field cooled state with sufficient ac field (few Oe).