Evidence of a first order like jump in equilibrium magnetization across   the peak effect region in superconducting 2H-NbSe$_2$
  We report magnetization hysteresis measurements in the peak effect region of a very clean single crystal of superconducting 2H-NbSe$_2$ at temperatures very close to T$_c$(0). Through measurement of minor magnetization curves, we infer the equilibrium magnetization curve across the PE region. We observe a small first order like change in equilibrium magnetization across the peak effect. We relate this observation to the entropy change associated with the order-disorder transformation. We further note that the first order like change in the equilibrium magnetization observed in 2H-NbSe$_2$ is comparable to the change(s)observed in the equilibrium magnetization at the FLL melting transition in various high temperature superconductors. 
G. Ravikumar et al