酸化物超伝導体の合成と評価 Ｃｕ３Ｏ４面を有する銅酸化物（Ｓｒ，Ｂａ）２Ｃｕ３Ｏ４（Ｃｌ，Ｂｒ）２へのキャリアドーピング

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 Ba2Cu3-xLixO4Cl2(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.