Electronic and magnetic properties of Cm in Pb2Sr2Cm1-xCaxCu3O8 (x=0.0 and 0.5)

A combination of x-ray diffraction, x-ray absorption spectroscopy, and magnetic susceptibility measurements have been used to study the physical properties of Pb₂Sr₂Cm_1-xCaₓCu₃O₈ $(x=0.0,0.5).$ These Cm compounds are isostructural with the superconducting members of the Pb₂Sr₂R_1-xCaₓCu₃O₈ (R denotes rare earth) series. X-ray absorption and magnetic susceptibility data clearly indicate that the Cm is trivalent in this compound, consistent with the superconducting members of this series. However, Pb₂Sr₂Cm0.5Ca0.5Cu₃O₈ is not superconducting. Furthermore, the Cm spins are found to magnetically order in the parent compound Pb₂Sr₂CmCu₃O₈ with an ordering temperature of 18 K. Suppression of superconductivity is observed together with high-magnetic ordering temperatures in other high-Tc related compounds synthesized with Cm. The results determined here are put into context with these previous observations.