Revealing the vortex order-disorder phase transition in smallBi2Sr2CaCu2O8+δcrystals

Abstract

The apparent absence of a vortex order-disorder phase transition in small ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ crystals is attributed to fast decay of bulk currents at relatively high temperatures, or to slow annealing of transient disordered vortex states at low temperatures, both obscuring the second magnetization peak that signifies the transition. Experimental procedures for compensating for these effects, leading to the emergence of a second magnetization peak in small samples, are demonstrated. Our results question previous reports on a size effect in the vortex matter phase transition.