Metastable vortex states inYBa2Cu3O7−δcrystal

Abstract

Magnetization measurements in an untwinned ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ crystal reveal a range of temperatures and fields for which the magnetization exhibits unusual history-dependent behavior. This range envelopes the transition line, ${B}_{\mathrm{ss}}(T),$ separating between the vortex quasiordered and disordered phases. The observed history effects indicate that a disordered (quasiordered) vortex state can exist as a metastable state below (above) the ${B}_{\mathrm{ss}}(T)$ line. The fields, defining the phase transition and the borders of the metastability region, are correlated to sharp features in the magnetization loop.