The suppression of superconductivity by the localization of oxygen holes in the double-doped La 1.85−1.5xSr 0.15+1.5xCu 1−xMn xO 4 system

Abstract

A series of double-doped La 1.85−1.5 x Sr 0.15+1.5 x Cu 1− x Mn x O 4 ( 0 ⩽ x ⩽ 0.2 ) samples were synthesized by the solid-state reaction method. The structural, transport and magnetic properties were studied. The superconductivity can even survive till Mn doping level to x = 0.15. It is noteworthy that the sample with x = 0.06 undergoes two superconducting transitions in the M– T curves. It is suggested that the Cu–O–Cu pdσ hybridization interaction is weakened by the superexchange interaction between the doped Mn ions and the O ions in the Cu–O–Cu paths neighboring Mn, which leads to the suppression of superconductivity.