Role of atomic modulation in the incommensurate composite crystal structure of (Sr2Cu2O3)0.70CuO2, “Sr14Cu24O41” with two-legged ladder and one-dimensional chain

Role of atomic modulation in the incommensurate composite crystal structure of (Sr2Cu2O3)0.70CuO2, “Sr14Cu24O41” has been investigated by four-dimensional superspace group approach. It has become apparent that the displacive modulations of Sr and O atoms are effective for the stabilization of alternate stacking of the planes of the Cu2O3 ladder and the CuO2 chain. The Cu-O bonds in both of the modulated and unmodulated structures have been investigated to understand the origin of electronic and magnetic properties. In the average structure, it has been clarified that considerable amount of holes are generated in the CuO2 chain. In the course of the modulated structure analysis, the Cu-O bond in the CuO2 chain has become tilt toward the Cu2O3 ladder in order that the O atom in the chain acts as apical oxygen for the ladder plane. By the large modulation of the O atom in the CuO2 chain, the prepared holes are distributed to make the hole-ordered structure in the CuO2 plane.