Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 10: Superconductivity: Fabrication and Characterization
TT 10.3: Vortrag
Montag, 25. Februar 2008, 14:30–14:45, H 3010
Effect of rare earth and alkaline earth substitutions in the superconductor RuA2RECu2O8 (RE=Gd, Eu, Nd, Pr; A=Ca, Sr, Ba): crystal structure and physical properties — •Eugenio Casini1,4, Consiglia Tedesco2, Antonio Vecchione2, Thomas P. Papageorgiou3, Hans F. Braun4, Manuel Kempf4, and Johannes Krämer4 — 1PANalytical, Almelo, The Netherlands — 2Università di Salerno, Italy — 3Forschungzentrum Dresden-Rossendorf, Germany — 4Universität Bayreuth, Germany
For small rare earth ions (RE=Gd, Eu), single phase compounds are obtained with the typical ordered layered structure and no significant changes of physical properties. With large rare earth ions (RE=Nd, Pr), polyphase samples were obtained and the phases in equilibrium at the nominal composition RuSr2RECu2O8 were determined. In these cases, no ordered layered structure was observed. The disorder between Ru/Cu or Sr/RE is presumably due to the similar Ru/Cu and Sr/RE ionic sizes. Magnetization studies of these compounds are discussed.
The effect of substituting Sr+2 with the smaller Ca+2 and larger Ba+2 is examined. The substitution with Ca+2 results in a complex mixture. We cannot confirm the previously reported formation of the layered RuCa2NdCu2O8. For Ba+2 substitution, a binary mixture Ba2RuNdO6–CuO is obtained. A different number and different types of phases in equilibrium are found with different alkaline earths (A=Ca, Sr, Ba) at the nominal RuA2NdCu2O8 composition. The variation in the mismatch of the A/Nd (A=Ca, Sr, Ba) size does not lead to the formation of an ordered layered RuA2NdCu2O8 compound.