Possible microscopic phase separation in the overdoped regime of La2-xSrxCuO4 studied by the magnetic susceptibility and electrical resistivity

Precise measurements of the magnetic susceptibility and the in-plane electrical resistivity in the overdoped regime of La2-xSrxCuO4 have been carried out using single crystals of good quality, in order to investigate the inhomogeneity of the superconductivity in the overdoped regime of high-T-c cuprates. From the magnetic-susceptibility measurements, it has been found that the Meissner volume fraction decreases with increasing x, indicating that phase separation into superconducting (SC) and normal-state regions takes place in the overdoped regime. From the in-plane resistivity measurements, it has been found that the SC transition width becomes broad with increasing x, which is possibly due to the increase of the volume fraction of the proximity region between SC and normal-state regions in the phase-separated CuO2 plane. It appears that microscopic phase separation takes place in the overdoped regime and that the proximity region becomes dominant with increase x. (C) 2007 Elsevier B.V. All rights reserved.