Carrier Doping into (Sr, Ba)₂Cu₃O₄(Cl, Br)₂ with the Cu₃O₄ Plane

Abstract

A trial of the carrier doping into (Sr, Ba)₂Cu₃O₄(Cl, Br)₂ with the Cu₃O₄ plane, which is composed of Cu(1)O₂ and extra Cu(2) sublattices, has been carried out through the partial substitution. We have succeeded in obtaining single-phase samples of Ba₂Cu_3-xLi_xO₄Cl₂(0≤x≤1.0). With increasing x, the α-axis tends to decrease and the c-axis is almost constant. All samples exhibit semiconductive behavior. The electrical resistivity decreases with increasing x up to 0.5 and tends to increase slightly for x>0.5 due to disorder in the Cu₃O₄ plane through the substitution of Li⁺ for Cu²⁺. Both of the antiferromagnetic transition temperatures with respect to Cu (1) and Cu (2) decrease with increasing x. However, the antiferromagnetic ordering in the Cu(1)O₂ sublattice still remains even for x=0.5. Considering that the formal valence of Cu is + 2.2 for x=0.5, holes doped through the Li-substitution maybe localized in the Cu(2) site. We will also discuss the possibility of the appearance of the superconductivity in the present system with the Cu₃O₄ plane.