Magnetic and transport properties in CoSr2Y1-xCaxCu2O7 (x=0-0.4) -: art. no. 054520

Magnetic and transport properties of CoSr2Y1-xCaxCu2O7 (x=0-0.4) system have been investigated. A broad maximum in the M(T) curve, indicative of low-dimensional antiferromagnetic ordering originated from CoO1+delta layers, is observed in the Ca-free sample. With increasing as Ca doping level up to 0.2, the M(T) curve remains almost unchanged, while resistivity is reduced by three orders. A higher Ca doping level leads to a drastic change of magnetic properties. In comparison with the samples with x=0.0-0.2, the temperature corresponding to the maximum of M(T) is much lower for the sample x=0.3. The sample x=0.4 shows a small kink instead of a broad maximum and a weak ferromagnetic feature. The electrical transport behavior is found to be closely related to magnetic properties for the sample x=0.2, 0.25, 0.3, 0.4. It suggests that CoO1+delta layers are involved in charge transport, in addition to conducting CuO2 planes to interpret the correlation between magnetism and charge transport. X-ray photoelectron spectroscopy studies give additional evidence of the the transfer of the holes into the CoO1+delta charge reservoir.