Peak effect studies in single crystals CeRu2 and 2H-NbS2

We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu 2 and 2H-NbS 2 . 2H-NbS 2 is iso-structural and iso-electronic to 2H-NbSe 2 , whose similarity with CeRu 2 as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We report on the step change in equilibrium magnetization across the peak effect in CeRu 2 . We also present the vortex phase diagram of 2H-NbS 2 obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS 2 and 2H-NbSe 2 .