Crossover from the vortex-lattice melting to the continuous transition in twinned NdBa 2Cu 3O y single crystals

Abstract

We report on the observation of the first-order melting transition of the flux line lattice in a twinned NdBa 2Cu 3O y single crystal by transport measurements. The magnetization J c does not exhibit peak effect in crystals grown up to 0.05% oxygen partial pressure. The observed melting transition is a strong function of O 2 partial pressure during growth. The first-order melting transition becomes continuous and peak in critical current density first emerges with oxygen partial pressure≥0.07%. Our results demonstrate the existence of a first-order melting transition in twinned RE-123 system containing rare-earth magnetic ions. We have shown that twin planes do not suppress the melting transition in the absence of defects due to Nd–Ba substitution.