Magnetic and Transport Properties in $CoS{r}_2{Y}_{1-x}C{a}_{x}C{u}_2{O}_7$ ($x$=0$\sim$0.4)

Abstract

Magnetic and transport properties of $CoS{r}_2{Y}_{1-x}C{a}_{x}C{u}_2{O}_7$ ($x=0\sim 0.4$) system have been investigated. A broad maximum in M(T) curve, indicative of low-dimensional antiferromagnetic ordering originated from $Co{O}_{1+\hat{I}´}$ layers, is observed in Ca-free sample. With increasing Ca doping level up to 0.2, the M(T) curve remains almost unchanged, while resistivity is reduced by three orders. Higher Ca doping level leads to a drastic change of magnetic properties. In comparison with the samples with $x=0.0\sim 0.2$, the temperature corresponding to the maximum of M(T) is much lowered 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 $Co{O}_{1+\hat{I}´}$ layers are involved in charge transport in addition to conducting $Cu{O}_2$ planes to interpret the correlation between magnetism and charge transport. X-ray photoelectron spectroscopy studies give an additional evidence of the the transfer of the holes into the $Co{O}_{1+\hat{I}´}$ charge reservoir.