We have confirmed that the (Sr0.4Ca0.6)14Cu24-xCo xO41-δ system with x = 0 has a spin gap of 735 K from NMR measurement. This system shows a metal-insulator transition at Co content x between 2.9 and 4.5 after high-pressure O2 annealing (650°C, 8 MPa, 20 h). The behavior of the electrical resistivity for the high-pressure O2 annealed sample with x = 4.8 can be characterized by the one-dimensional variable range hopping scheme at low temperature. These facts can be interpreted as the trapped hole carriers in the 1D CuO2 chain being released into the ladder by Co doping x above 2.9 under high-pressure O2 annealing.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering