Superconducting Volume Fraction in Overdoped Regime of La_2-<i>x</i>Sr_<i>x</i>CuO₄: Implication for Phase Separation from Magnetic-Susceptibility Measurement

Abstract

We have grown a single crystal of La_2-x_Sr_x_CuO_4_ in which the Sr\nconcentration, x, continuously changes from 0.24 to 0.29 in the overdoped\nregime and obtained many pieces of single crystals with different x values by\nslicing the single crystal. From detailed measurements of the magnetic\nsusceptibility, chi, of each piece, it has been found that the absolute value\nof chi at the measured lowest temperature 2 K, |chi_2K_|, on field cooling\nrapidly decreases with increasing x as well as the superconducting (SC)\ntransition temperature. As the value of |chi_2K_| is regarded as corresponding\nto the SC volume fraction in a sample, it has been concluded that a phase\nseparation into SC and normal-state regions occurs in a sample of\nLa_2-x_Sr_x_CuO_4_ in the overdoped regime.\n