Superconducting Volume Fraction in Overdoped Regime of La_2−xSr_xCuO₄: Implication for Phase Separation from Magnetic-Susceptibility Measurement

Abstract

We have grown a single crystal of La_2−xSr_xCuO₄ in which the Sr concentration, x, continuously changes from 0.24 to 0.29 in the overdoped regime and obtained many pieces of single crystals with different x values by slicing the single crystal. From detailed measurements of the magnetic susceptibility, χ, of each piece, it has been found that the absolute value of χ at the measured lowest temperature 2 K, |χ_{2 K}|, on field cooling rapidly decreases with increasing x as well as the superconducting (SC) transition temperature. As the value of |χ_{2 K}| is regarded as corresponding to the SC volume fraction in a sample, it has been concluded that a phase separation into SC and normal-state regions occurs in a sample of La_2−xSr_xCuO₄ in the overdoped regime.