Oxidation states of the ''unusual'' rare earths (R=Ce, Pr and Tb) in double layer high-T(sub c) superconductors

摘要

X-ray absorption and magnetization experiments are used to describe the oxidation states of the rare earths R= Ce, Pr, and Tb in the double layer high-Tc superconducting series RBa(sub 2)Cu(sub 3)O(sub 7) and Pb(sub 2)Sr(sub 2)R(sub 1-x)Ca(sub x)Cu(sub 3)O(sub 8). We obtained the same oxidation states for the rare earths in these two classes of compounds, namely, R=Ce tetravalent and R=Pr and Tb trivalent.