Oxygen hole-doping effects on the spin-chain system Ca_{2 + x} Y_{2 - x} Cu₅ O_{10 - δ}

The magnetic properties of the low-dimensional spin-chain system Ca_{2 + x} Y_{2 - x} Cu₅ O_{10 - δ} were studied as a function of oxygen content and Ca-doping. A series of samples with different oxygen contents were prepared by solid state reaction under various oxygen pressures up to 170 atm and characterized by X-ray diffraction and iodometric titration. Oxygen deficiency was observed to be from δ = 0.2 - 0.4 at 0.2 atm to δ ≈ 0.0 at 170 atm oxygen pressure. Oxygen deficiency increases with Ca-doping at fixed oxygen pressure. The temperature dependence of the magnetic moment and of the specific heat are reported here for the x = 0.9 sample with various oxygen deficiencies. The effects of oxygen deficiency on magnetic coupling are compared with Ca-doping. Notably, oxygen content plays a much more critical role in the reduction of magnetic interactions in the CuO₂ chains than Ca-doping, even for the same hole concentration.