Inhomogeneity of superconductivity and stripe correlations at x ∼ 0.21 in La_2-xSr_xCuO₄

With the aim at investigating the relationship between the anomalous decrease in T_c, the development of the Cu-spin correlation and the inhomogeneity of superconductivity at x ∼ 0.21 in the overdoped regime of La_2-xSr_xCuO₄, we have performed the in-plane electrical-resistivity, ρ_ab and magnetization measurements. Measurements of the temperature dependence of ρ_ab in magnetic fields have revealed that the superconducting (SC) transition curve shifts to the low-temperature side almost in parallel with increasing field above ∼ 9 T at x ∼ 0.21, which is similar to that observed for stripe-ordered La-214 systems with the hole concentration of ∼ 1/8 per Cu. On the other hand, it has been found that the magnetization curve shows the so-called second peak in the SC state at x ∼ 0.21, which is due to the strong vortex pinning in normal-state regions in the nano-scale inhomogeneous SC state. Accordingly, it is likely that the stripe correlations are developed in the nano-scale inhomogeneous SC state at x ∼ 0.21.