Vortex decoupling line and its anisotropy in Bi₂Sr₂CaCu₂O_8+δ single crystals observed by J_c(H, T, θ) transport current measurements

Transport critical current densities in single crystals of the strongly anisotropic high-T_c superconductor Bi₂Sr₂CaCu₂O_8+δ were measured in a wide range of temperature, applied field and angles between field direction and c-axis of the crystals, above and below the decoupling line. In the low-field region, below the decoupling line, an analysis of the field and angle dependences of the J_c allows us to assume a dominance of the collective pinning mechanism, which is similar to that found in moderately anisotropic YBa₂Cu₃O_7-δ single crystals. We provide scaling analysis of the J_c(H, T, θ) dependences to probe the vortex topology and to locate the decoupling line on the H-T-θ diagram.