The suppression of superconductivity by the localization of oxygen holes in the double-doped La1.85−1.5xSr0.15+1.5xCu1−xMnxO4 system

► The transport and magnetic properties for mixed-valence Mn doped LSCO were studied. ► The superconductivity can even survive till Mn doping level to x = 0.15. ► There are two superconducting transitions at x = 0.06 in the M-T curves. ► The pdσ hybridization is weakened by the superexchange between doped Mn and O ions. ► This weakened pdσ hybridization leads to the suppression of superconductivity.