Supercooling of the disordered vortex phase via minor hysteresis loops in 2H-NbSe2

We report on the observation of novel features in the minor hysteresis loop s in a clean crystal of 2H-NbSe2, which displays a peak effect. The observe d behavior can be explained in terms of a supercooling of the disordered vo rtex phase while cooling the superconductor in a field. Also, the extent of spatial order in a flux-line lattice formed in ascending fields is differe nt from (and larger than) that in the descending fields below the peak posi tion of the peak effect; this is attributed to a different degree of reorga nization of the vortex state induced by changes in the field in the two cas es.