We have investigated the transport and magnetic properties of Sr14-xAxCu24O41 (m = Ca, Ba, Y, La) consisting of two-dimensional Cu2O3 planes, namely, so-called spin-ladders with two legs and also of one-dimensional CuO2 chains. Sr14Cu24O41 exhibits a semiconductive behavior. For x(Ca) ≧ 8.4, metallic behavior is observed in the thermoelectric power measurements, but superconductivity does not appear. The susceptibility exhibits a broad peak around 80 K for x = 0. With incresing x, the Curie component at low temperatures increases and the broad peak disappears. It has been concluded that the broad peak is due to spin gap of the CuO2 chains and that the Cu2+ spins in the Cu2O3 planes have already formed spin-singlet pairs below room temperature. A model on the spin configuration in the CuO2 chains at low temperatures is proposed, depending on the value of x.
ASJC Scopus subject areas
- Physics and Astronomy(all)