Effect of oxygen-doping onBi2Sr2Ca2Cu3O10+δvortex matter: Crossover from electromagnetic to Josephson interlayer coupling

Abstract

We study the effect of oxygen-doping on the critical temperature ${T}_{c}$, the vortex matter phase diagram, and the nature of the coupling mechanism between the Cu-O layers in the three-layer ${\text{Bi}}_{2}{\text{Sr}}_{2}{\text{Ca}}_{2}{\text{Cu}}_{3}{\text{O}}_{10+\ensuremath{\delta}}$ (Bi-2223) compound. Contrary to previous reports, in the overdoped (OD) regime, we do find a variation in ${T}_{c}$ by increasing the oxygen partial pressure of the postannealing treatment. This variation is less significant than in the bilayer compound ${\text{Bi}}_{2}{\text{Sr}}_{2}{\text{CaCu}}_{2}{\text{O}}_{10+\ensuremath{\delta}}$ (Bi-2212) and does not follow the universal ${T}_{c}$ vs $\ensuremath{\delta}$ relation. Magnetic measurements reveal that increasing $\ensuremath{\delta}$ enlarges the field and temperature stability of the Bragg glass phase. These findings imply that the interlayer coupling between Cu-O layers enhances with $\ensuremath{\delta}$. The anisotropy parameter estimated from directional first-penetration field measurements monotonously decreases from 50 in the underdoped (UD) to 15 in the OD regimes. However, the in-plane penetration depth presents a boomerang-type behavior with $\ensuremath{\delta}$, reaching its minimum value close to optimal doping. These two facts lead to a crossover from a Josephson OD to electromagnetic UD-dominated coupling of adjacent Cu-O layers in the vicinity of optimal doping.